diff --git a/runtime/doc/deprecated.txt b/runtime/doc/deprecated.txt
index bd3835f451..ecdab2df68 100644
--- a/runtime/doc/deprecated.txt
+++ b/runtime/doc/deprecated.txt
@@ -33,10 +33,16 @@ HIGHLIGHTS
 
 LUA
 
-• vim.F.if_nil()			Renamed to |vim.nonnil()|
+• vim.F.if_nil()		Renamed to |vim.nonnil()|
 • vim.F.ok_or_nil()
-• vim.F.npcall()			Renamed to |vim.npcall()|
-• vim.F.nil_wrap()			Use |vim.npcall()| instead
+• vim.F.npcall()		Renamed to |vim.npcall()|
+• vim.F.nil_wrap()		Use |vim.npcall()| instead
+• *vim.uri_decode()*		Renamed to |vim.uri.decode()|
+• *vim.uri_encode()*		Renamed to |vim.uri.encode()|
+• *vim.uri_from_bufnr()*	Renamed to |vim.uri.from_buf()|
+• *vim.uri_from_fname()*	Renamed to |vim.uri.from_fname()|
+• *vim.uri_to_bufnr()*		Renamed to |vim.uri.to_buf()|
+• *vim.uri_to_fname()*		Renamed to |vim.uri.to_fname()|
 
 TREESITTER
 
diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 77e748d005..9df50386de 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -2691,7 +2691,8 @@ vim.fs.abspath({path}, {opts})                              *vim.fs.abspath()*
     the path (unless plain=true). Does not check if the path exists, normalize
     the path, resolve symlinks or hardlinks (including "." and ".."), or
     expand environment variables. If the path is already absolute, it is
-    returned unchanged. Converts `\` path separators to `/`.
+    returned unchanged. Converts `\` path separators to `/`. URLs (e.g.
+    "fugitive:///a") are returned as-is.
 
     Attributes: ~
         Since: 0.11.0
@@ -3030,9 +3031,9 @@ vim.fs.root({source}, {marker})                                *vim.fs.root()*
         Since: 0.10.0
 
     Parameters: ~
-      • {source}  (`integer|string`) Buffer number (0 for current buffer) or
-                  file path (absolute or relative, expanded via `abspath()`)
-                  to begin the search from.
+      • {source}  (`integer|string`) Buffer number (0 for current buffer),
+                  file path (absolute or relative, expanded via `abspath()`),
+                  or "file://" URI to begin the search from.
       • {marker}  (`(string|string[]|fun(name: string, path: string): boolean)[]|string|fun(name: string, path: string): boolean`)
                   Filename, function, or list thereof, that decides how to
                   find the root. To indicate "equal priority", specify items
@@ -5868,8 +5869,24 @@ vim.ui.img.set({data_or_id}, {opts})                        *vim.ui.img.set()*
 ==============================================================================
 Lua module: vim.uri                                                  *vim.uri*
 
-vim.uri_decode({str})                                       *vim.uri_decode()*
-    URI-decodes a string containing percent escapes.
+vim.Uri                                                              *vim.Uri*
+
+    Fields: ~
+      • {authority}?  (`string`) Authority (after "//"), e.g.
+                      "user@example.com:8080". Empty for "file:///a", nil for
+                      "file:/a".
+      • {fragment}?   (`string`) Fragment (after "#"), e.g. "section".
+      • {path}        (`string`) Path, e.g. "/a/b". Empty for
+                      "https://example.com".
+      • {query}?      (`string`) Query (after "?"), e.g. "q=1".
+      • {scheme}      (`string`) Scheme, e.g. "https".
+
+
+vim.uri.decode({str})                                       *vim.uri.decode()*
+    Decodes a URI-encoded string.
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {str}  (`string`) string to decode
@@ -5877,8 +5894,11 @@ vim.uri_decode({str})                                       *vim.uri_decode()*
     Return: ~
         (`string`) decoded string
 
-vim.uri_encode({str}, {rfc})                                *vim.uri_encode()*
-    URI-encodes a string using percent escapes.
+vim.uri.encode({str}, {rfc})                                *vim.uri.encode()*
+    URI-encodes a string.
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {str}  (`string`) string to encode
@@ -5887,8 +5907,11 @@ vim.uri_encode({str}, {rfc})                                *vim.uri_encode()*
     Return: ~
         (`string`) encoded string
 
-vim.uri_from_bufnr({buf})                               *vim.uri_from_bufnr()*
-    Gets a URI from a bufnr.
+vim.uri.from_buf({buf})                                   *vim.uri.from_buf()*
+    Gets a URI from a buffer.
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {buf}  (`integer`)
@@ -5896,8 +5919,19 @@ vim.uri_from_bufnr({buf})                               *vim.uri_from_bufnr()*
     Return: ~
         (`string`) URI
 
-vim.uri_from_fname({path})                              *vim.uri_from_fname()*
-    Gets a URI from a file path.
+vim.uri.from_fname({path})                              *vim.uri.from_fname()*
+    Gets a URI from a file path. Relative paths are resolved to
+    |current-directory| (RFC 8089 disallows relative URIs).
+
+    Example: >lua
+        vim.uri.from_fname('/a b/c#') --> 'file:///a%20b/c%23'
+        vim.uri.from_fname('C:\\a\\b') --> 'file:///C:/a/b'
+        vim.uri.from_fname('//server/share/a') --> 'file://server/share/a' (UNC)
+        vim.uri.from_fname('a') --> 'file:///home/user/a' (if CWD is "/home/user")
+<
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {path}  (`string`) Path to file
@@ -5905,18 +5939,53 @@ vim.uri_from_fname({path})                              *vim.uri_from_fname()*
     Return: ~
         (`string`) URI
 
-vim.uri_to_bufnr({uri})                                   *vim.uri_to_bufnr()*
-    Gets the buffer for a uri. Creates a new unloaded buffer if no buffer for
-    the uri already exists.
+vim.uri.parse({uri})                                         *vim.uri.parse()*
+    Parses a URI into its RFC 3986 components, without decoding them. Unlike
+    RFC 3986, a one-letter scheme is a drive letter, so `C:/a` is not a URI.
+
+    Example: >lua
+        vim.uri.parse('https://example.com/a%20b?q=1#section')
+        --> { scheme = 'https', authority = 'example.com', path = '/a%20b', query = 'q=1', fragment = 'section' }
+        vim.uri.parse('/a/b') --> nil
+        vim.uri.parse('C:/a') --> nil
+        tostring(vim.uri.parse('file:///a?b')) --> 'file:///a?b'
+<
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {uri}  (`string`)
 
     Return: ~
-        (`integer`) bufnr
+        (`vim.Uri?`) URI components, or nil if `uri` has no scheme.
 
-vim.uri_to_fname({uri})                                   *vim.uri_to_fname()*
-    Gets a filename from a URI.
+vim.uri.to_buf({uri})                                       *vim.uri.to_buf()*
+    Gets the buffer for a uri. Creates a new unloaded buffer if no buffer for
+    the uri already exists.
+
+    Attributes: ~
+        Since: 0.13.0
+
+    Parameters: ~
+      • {uri}  (`string`)
+
+    Return: ~
+        (`integer`) buf
+
+vim.uri.to_fname({uri})                                   *vim.uri.to_fname()*
+    Gets a filename from a URI. Drops the query and fragment, so "?" and "#"
+    in a filename must be percent-encoded.
+
+    Example: >lua
+        vim.uri.to_fname('file:///a%3Fb?c#d') --> '/a?b'
+        vim.uri.to_fname('file:///C:/a/b') --> 'C:/a/b'
+        vim.uri.to_fname('file://server/share/a') --> '//server/share/a'
+        vim.uri.to_fname('jdt://a/b') --> 'jdt://a/b'
+<
+
+    Attributes: ~
+        Since: 0.13.0
 
     Parameters: ~
       • {uri}  (`string`)
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index cf58321845..29fcb5abbf 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -45,6 +45,11 @@ LUA
     `{ key = value }` instead of an array of `"key:value"` strings.
   - The `,,` literal-comma convention (e.g. 'isfname') is not reconstructed in
     the structured view; the raw string value is unchanged.
+• Backslashes are not supported in URIs/URLs. E.g. "http:\\host" is treated as
+  a filepath, not a URL, in buffer names, |gf|, etc.
+• |vim.uri.to_fname()| returns "/" separators (also on Windows), drops the URI
+  query, and converts a URI host to a UNC path ("file://server/share" =>
+  "//server/share").
 
 DIAGNOSTICS
 
@@ -438,6 +443,8 @@ LUA
 • |vim.pos.cursor()| without arguments returns the cursor position of the
   current window.
 • |vim.ui.input()| now allows setting input scope.
+• |vim.uri| is a module. The old `uri_xx` top-level functions were renamed,
+  e.g. `vim.uri_to_fname()` is now |vim.uri.to_fname()|.
 • |vim.log| provides a logging interface.
 • |vim.pack.get()| output includes revision of a pending update.
 • |vim.pack.get()| can fetch new updates before computing the output.
@@ -600,6 +607,10 @@ These existing features changed their behavior.
   `opts.plain=true` and now does not expand leading tildes ("~") in addition
   to environment variables ("expand_env" is still accepted, for backwards
   compatibility).
+• |vim.fs.abspath()| returns URLs (e.g. "fugitive:///a") as-is, so
+  |vim.filetype.add()| functions receive URI buffer names unchanged.
+• |vim.uri.from_fname()| resolves relative paths to absolute paths, and
+  converts UNC paths.
 • |:helptags| finds help tags with the "vimdoc" |treesitter| parser (and thus
   requires it to be installed).
 • `:helptags ALL` reports |E152| for "doc" directories it cannot write,
diff --git a/runtime/ftplugin/help.lua b/runtime/ftplugin/help.lua
index 4ad3a0c66a..d5af341091 100644
--- a/runtime/ftplugin/help.lua
+++ b/runtime/ftplugin/help.lua
@@ -156,7 +156,7 @@ local function urls()
             vim.api.nvim_buf_set_extmark(0, url_ns, start_line, start_col, {
               end_line = end_line,
               end_col = end_col,
-              url = base .. vim.uri_encode(tag),
+              url = base .. vim.uri.encode(tag),
             })
           end
         end
diff --git a/runtime/lua/nvim/dir/fs.lua b/runtime/lua/nvim/dir/fs.lua
index 9ff95ce8ad..688954c941 100644
--- a/runtime/lua/nvim/dir/fs.lua
+++ b/runtime/lua/nvim/dir/fs.lua
@@ -2,6 +2,7 @@
 
 local api = vim.api
 local fs = vim.fs
+local is_url = vim._core.path_is_url
 
 local M = {}
 
@@ -48,7 +49,7 @@ end
 
 ---@param path string
 function M.open_parent_path(path)
-  if path == '' or path:find('^%a[%w+.-]*://') then
+  if path == '' or is_url(path) then
     navigate('.')
     return
   end
diff --git a/runtime/lua/nvim/zip.lua b/runtime/lua/nvim/zip.lua
index c319c6a269..32e1f4b590 100644
--- a/runtime/lua/nvim/zip.lua
+++ b/runtime/lua/nvim/zip.lua
@@ -1,6 +1,7 @@
 local api = vim.api
 local uv = vim.uv
 local notify = require('vim._core.util').notify
+local is_url = vim._core.path_is_url
 
 local M = {}
 
@@ -530,7 +531,7 @@ function M.open_parent(buf, name)
     require('nvim.dir').open(buf, name, M, { name = child, dir = true })
     return
   end
-  if name:match('^%a[%w+.-]*://') then
+  if is_url(name) then
     return
   end
   require('nvim.dir.fs').open_parent_path(state.source)
diff --git a/runtime/lua/vim/_core/editor.lua b/runtime/lua/vim/_core/editor.lua
index d6457cc3e1..5a02f3075c 100644
--- a/runtime/lua/vim/_core/editor.lua
+++ b/runtime/lua/vim/_core/editor.lua
@@ -31,13 +31,9 @@ for k, v in pairs({
 end
 
 -- There are things which have special rules in vim._init_packages
--- for legacy reasons (uri) or for performance (_inspector).
+-- for performance (_inspector).
 -- most new things should go into a submodule namespace ( vim.foobar.do_thing() )
 vim._extra = {
-  uri_from_fname = true,
-  uri_from_bufnr = true,
-  uri_to_fname = true,
-  uri_to_bufnr = true,
   show_pos = true,
   inspect_pos = true,
 }
diff --git a/runtime/lua/vim/_init_packages.lua b/runtime/lua/vim/_init_packages.lua
index 5108a9fe70..a0dfcd2729 100644
--- a/runtime/lua/vim/_init_packages.lua
+++ b/runtime/lua/vim/_init_packages.lua
@@ -53,15 +53,26 @@ end
 require('vim._core.shared')
 
 vim._submodules = {
-  inspect = true,
-  version = true,
   fs = true,
   glob = true,
+  inspect = true,
   iter = true,
+  provider = true,
   re = true,
   text = true,
   tty = true,
-  provider = true,
+  uri = true,
+  version = true,
+}
+
+--- Deprecated aliases of `vim.uri` functions.
+local uri_aliases = {
+  uri_decode = 'decode',
+  uri_encode = 'encode',
+  uri_from_bufnr = 'from_buf',
+  uri_from_fname = 'from_fname',
+  uri_to_bufnr = 'to_buf',
+  uri_to_fname = 'to_fname',
 }
 
 -- These are for loading runtime modules in the vim namespace lazily.
@@ -74,14 +85,16 @@ setmetatable(vim, {
     elseif key == 'inspect_pos' or key == 'show_pos' then
       require('vim._inspector')
       return t[key]
-    elseif vim.startswith(key, 'uri_') then
-      --- @type any?
-      local val = require('vim.uri')[key]
-      if val ~= nil then
-        -- Expose all `vim.uri` functions on the `vim` module.
-        t[key] = val
-        return t[key]
+    elseif uri_aliases[key] then
+      local name = uri_aliases[key]
+      local fn = require('vim.uri')[name] --- @type function
+      t[key] = function(...)
+        if not vim.is_thread() then
+          vim.deprecate(('vim.%s'):format(key), ('vim.uri.%s'):format(name), '0.15')
+        end
+        return fn(...)
       end
+      return t[key]
     end
   end,
 })
diff --git a/runtime/lua/vim/_meta.lua b/runtime/lua/vim/_meta.lua
index 6ae800e958..a19e4349d4 100644
--- a/runtime/lua/vim/_meta.lua
+++ b/runtime/lua/vim/_meta.lua
@@ -37,13 +37,20 @@ vim.text = require('vim.text')
 vim.treesitter = require('vim.treesitter')
 vim.tty = require('vim.tty')
 vim.ui = require('vim.ui')
+vim.uri = require('vim.uri')
 vim.version = require('vim.version')
 
-local uri = require('vim.uri')
-
-vim.uri_from_fname = uri.uri_from_fname
-vim.uri_from_bufnr = uri.uri_from_bufnr
-vim.uri_to_fname = uri.uri_to_fname
-vim.uri_to_bufnr = uri.uri_to_bufnr
+--- @deprecated
+vim.uri_decode = vim.uri.decode
+--- @deprecated
+vim.uri_encode = vim.uri.encode
+--- @deprecated
+vim.uri_from_bufnr = vim.uri.from_buf
+--- @deprecated
+vim.uri_from_fname = vim.uri.from_fname
+--- @deprecated
+vim.uri_to_bufnr = vim.uri.to_buf
+--- @deprecated
+vim.uri_to_fname = vim.uri.to_fname
 
 vim.provider = require('vim.provider')
diff --git a/runtime/lua/vim/_meta/builtin.lua b/runtime/lua/vim/_meta/builtin.lua
index fe45546acd..118799e724 100644
--- a/runtime/lua/vim/_meta/builtin.lua
+++ b/runtime/lua/vim/_meta/builtin.lua
@@ -197,6 +197,13 @@ function vim._core.loop_poll(timeout, fast_only) end
 --- Flushes pending UI updates.
 function vim._core.ui_flush() end
 
+--- @nodoc
+--- (C function: `path_with_url()`) Checks if `name` is a URL (not a file path): "deno:/a" and
+--- "fugitive:///a" are URLs, "C:/a" and "mailto:a" are not.
+--- @param name string
+--- @return boolean
+function vim._core.path_is_url(name) end
+
 --- @nodoc
 --- Checks for interrupt, clears it, and consumes input if present.
 --- @return boolean
diff --git a/runtime/lua/vim/diagnostic/_float.lua b/runtime/lua/vim/diagnostic/_float.lua
index 2cca7784ba..85da04d2cc 100644
--- a/runtime/lua/vim/diagnostic/_float.lua
+++ b/runtime/lua/vim/diagnostic/_float.lua
@@ -218,7 +218,7 @@ function M.open(opts, ...)
     -- range, plus description.
     for _, info in ipairs(related_info) do
       local location = info.location
-      local file_name = vim.fs.basename(vim.uri_to_fname(location.uri))
+      local file_name = vim.fs.basename(vim.uri.to_fname(location.uri))
       local info_suffix = ': ' .. info.message
       related_info_locations[#lines + 1] = location
       lines[#lines + 1] = string.format(
diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index 4cd2c92b60..4f0dbd8664 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -1,5 +1,6 @@
 local api = vim.api
 local fn = vim.fn
+local is_url = vim._core.path_is_url
 
 local M = {}
 
@@ -3286,7 +3287,7 @@ function M.match(args)
   end
 
   if name then
-    if name:sub(-1) == '/' and not name:find('^%a[%w+.-]*://') then
+    if name:sub(-1) == '/' and not is_url(name) then
       return 'directory'
     end
     name = normalize_path(name)
diff --git a/runtime/lua/vim/fs.lua b/runtime/lua/vim/fs.lua
index 4401541a55..7ae4c5367f 100644
--- a/runtime/lua/vim/fs.lua
+++ b/runtime/lua/vim/fs.lua
@@ -41,6 +41,14 @@
 --- ```
 
 local uv = vim.uv
+local uri_parse = require('vim.uri').parse
+
+--- @param path string
+--- @return boolean
+local function is_url(path)
+  -- XXX: always false in nlua0 (build-time generators), which has no C bindings.
+  return vim._core ~= nil and vim._core.path_is_url(path)
+end
 
 local M = {}
 
@@ -187,7 +195,8 @@ function M.slug(path, opts)
   local maxlen = opts.maxlen or 180
 
   -- Capture URI scheme before normalize() collapses "://" to ":/" (which looks like "C:/")
-  local uri_scheme = path:match('^([a-zA-Z][a-zA-Z0-9.+-]*)://') ---@type string?
+  local uri = uri_parse(path)
+  local uri_scheme = uri and uri.authority and uri.scheme
 
   -- Normalize before computing the hash so equivalent paths produce the same result
   path = vim.fs.normalize(path, { plain = true })
@@ -628,8 +637,8 @@ end
 --- ```
 ---
 --- @since 12
---- @param source integer|string Buffer number (0 for current buffer) or file path (absolute or
----               relative, expanded via `abspath()`) to begin the search from.
+--- @param source integer|string Buffer number (0 for current buffer), file path (absolute or
+---               relative, expanded via `abspath()`), or "file://" URI to begin the search from.
 --- @param marker (string|string[]|fun(name: string, path: string): boolean)[]|string|fun(name: string, path: string): boolean
 ---               Filename, function, or list thereof, that decides how to find the root. To
 ---               indicate "equal priority", specify items in a nested list `{ { 'a.txt', 'b.lua' }, … }`.
@@ -654,6 +663,12 @@ function M.root(source, marker)
   else
     error('invalid type for argument "source": expected string or buffer number')
   end
+  local uri = uri_parse(path)
+  if uri and uri.scheme:lower() == 'file' then
+    path = vim.uri.to_fname(path)
+  elseif is_url(path) then
+    path = assert(uv.cwd())
+  end
 
   local markers = type(marker) == 'table' and marker or { marker }
   for _, mark in ipairs(markers) do
@@ -1012,7 +1027,8 @@ end
 --- Converts `path` to an absolute path. Expands tilde (~) at the beginning of the path (unless
 --- plain=true). Does not check if the path exists, normalize the path, resolve symlinks or
 --- hardlinks (including "." and ".."), or expand environment variables. If the path is already
---- absolute, it is returned unchanged. Converts `\` path separators to `/`.
+--- absolute, it is returned unchanged. Converts `\` path separators to `/`. URLs (e.g.
+--- "fugitive:///a") are returned as-is.
 ---
 --- @since 13
 --- @param path string Path
@@ -1027,6 +1043,10 @@ function M.abspath(path, opts)
   vim.validate('cwd', opts.cwd, 'string', true)
   vim.validate('plain', opts.plain, 'boolean', true)
 
+  if is_url(path) then
+    return path
+  end
+
   -- Expand ~ to user's home directory
   if not opts.plain then
     path = expand_home(path)
diff --git a/runtime/lua/vim/health/health.lua b/runtime/lua/vim/health/health.lua
index 0bec0220c6..1f666eb48d 100644
--- a/runtime/lua/vim/health/health.lua
+++ b/runtime/lua/vim/health/health.lua
@@ -824,7 +824,7 @@ local function check_sysinfo()
     if win == -1 then
       return
     end
-    local encoded_body = vim.uri_encode(body) --- @type string
+    local encoded_body = vim.uri.encode(body) --- @type string
     local issue_url = 'https://github.com/neovim/neovim/issues/new?type=Bug&body=' .. encoded_body
 
     --- Opens the prefilled issue from the checkhealth winbar.
diff --git a/runtime/lua/vim/loader.lua b/runtime/lua/vim/loader.lua
index 9123a68a77..a445ed2894 100644
--- a/runtime/lua/vim/loader.lua
+++ b/runtime/lua/vim/loader.lua
@@ -1,6 +1,6 @@
 local fs = vim.fs -- "vim.fs" is a dependency, so must be loaded early.
 local uv = vim.uv
-local uri_encode = vim.uri_encode --- @type function
+local uri_encode = vim.uri.encode --- @type function
 
 --- @type (fun(modename: string): fun()|string)[]
 local loaders = package.loaders
diff --git a/runtime/lua/vim/lsp.lua b/runtime/lua/vim/lsp.lua
index ca74350b05..dd00534199 100644
--- a/runtime/lua/vim/lsp.lua
+++ b/runtime/lua/vim/lsp.lua
@@ -60,7 +60,7 @@ function lsp._get_workspace_folders(workspace_folders)
   elseif type(workspace_folders) == 'string' then
     return {
       {
-        uri = vim.uri_from_fname(workspace_folders),
+        uri = vim.uri.from_fname(workspace_folders),
         name = workspace_folders,
       },
     }
@@ -916,7 +916,7 @@ local function buf_attach(bufnr)
   end
   attached_buffers[bufnr] = true
 
-  local uri = vim.uri_from_bufnr(bufnr)
+  local uri = vim.uri.from_buf(bufnr)
   local augroup = ('nvim.lsp.b_%d_save'):format(bufnr)
   local group = api.nvim_create_augroup(augroup, { clear = true })
   nvim_on('BufWritePre', group, {
diff --git a/runtime/lua/vim/lsp/_changetracking.lua b/runtime/lua/vim/lsp/_changetracking.lua
index f68f8dd505..defa70b382 100644
--- a/runtime/lua/vim/lsp/_changetracking.lua
+++ b/runtime/lua/vim/lsp/_changetracking.lua
@@ -182,7 +182,7 @@ function M._send_did_save(bufnr)
     table.insert(entry.clients, client)
   end
 
-  local uri = vim.uri_from_bufnr(bufnr)
+  local uri = vim.uri.from_buf(bufnr)
   local text = vim.func._memoize('concat', vim.lsp._buf_get_full_text)
 
   -- Send didOpen/didClose/didSave to all client groups.
@@ -197,7 +197,7 @@ function M._send_did_save(bufnr)
       if old_name and name ~= old_name then
         client:notify('textDocument/didClose', {
           textDocument = {
-            uri = vim.uri_from_fname(old_name),
+            uri = vim.uri.from_fname(old_name),
           },
         }, bufnr)
         client:notify('textDocument/didOpen', {
@@ -325,7 +325,7 @@ local function send_changes(bufnr, sync_kind, state, buf_state)
       { text = vim.lsp._buf_get_full_text(bufnr) },
     }
   end
-  local uri = vim.uri_from_bufnr(bufnr)
+  local uri = vim.uri.from_buf(bufnr)
   for _, client in pairs(state.clients) do
     if not client:is_stopped() and vim.lsp.buf_is_attached(bufnr, client.id) then
       client:notify('textDocument/didChange', {
diff --git a/runtime/lua/vim/lsp/_watchfiles.lua b/runtime/lua/vim/lsp/_watchfiles.lua
index 465f75a7a7..230bdcb115 100644
--- a/runtime/lua/vim/lsp/_watchfiles.lua
+++ b/runtime/lua/vim/lsp/_watchfiles.lua
@@ -69,11 +69,11 @@ local function watcher_rules(watchers, workspace_folders)
     if type(pattern) == 'string' then
       for _, folder in ipairs(workspace_folders) do
         rules[#rules + 1] =
-          { path = vim.uri_to_fname(folder.uri), pattern = pattern, events = events }
+          { path = vim.uri.to_fname(folder.uri), pattern = pattern, events = events }
       end
     else
       local uri = type(pattern.baseUri) == 'string' and pattern.baseUri or pattern.baseUri.uri
-      local base = vim.uri_to_fname(uri)
+      local base = vim.uri.to_fname(uri)
       local prefix = vim.fs.normalize(base):gsub('/$', '')
 
       rules[#rules + 1] = {
@@ -117,7 +117,7 @@ local function queue_change(client, fullpath, change_type)
   local client_id = client.id
   --- @type lsp.FileEvent
   local change = {
-    uri = vim.uri_from_fname(fullpath),
+    uri = vim.uri.from_fname(fullpath),
     type = to_lsp_change_type[change_type],
   }
 
diff --git a/runtime/lua/vim/lsp/client.lua b/runtime/lua/vim/lsp/client.lua
index 5f38ddab59..3410a184fd 100644
--- a/runtime/lua/vim/lsp/client.lua
+++ b/runtime/lua/vim/lsp/client.lua
@@ -551,7 +551,7 @@ function Client:initialize()
   local workspace_folder = self.workspace_folders and self.workspace_folders[1]
   if workspace_folder then
     root_uri = workspace_folder.uri
-    root_path = vim.uri_to_fname(root_uri)
+    root_path = vim.uri.to_fname(root_uri)
   end
 
   -- HACK: Capability modules must be loaded
@@ -1106,8 +1106,8 @@ function Client:_get_registrations(provider, bufnr)
       matched_regs[#matched_regs + 1] = reg
     else
       local language = self:_get_language_id(bufnr)
-      local uri = vim.uri_from_bufnr(bufnr)
-      local fname = vim.uri_to_fname(uri)
+      local uri = vim.uri.from_buf(bufnr)
+      local fname = vim.uri.to_fname(uri)
       for _, filter in ipairs(regoptions.documentSelector) do
         local flang, fscheme, fpat = filter.language, filter.scheme, filter.pattern
         if
@@ -1179,7 +1179,7 @@ function Client:_text_document_did_close_handler(bufnr)
   if not self:supports_method('textDocument/didClose') then
     return
   end
-  local uri = vim.uri_from_bufnr(bufnr)
+  local uri = vim.uri.from_buf(bufnr)
   local params = { textDocument = { uri = uri } }
   self:notify('textDocument/didClose', params, bufnr)
 end
@@ -1199,7 +1199,7 @@ function Client:_text_document_did_open_handler(bufnr)
   self:notify('textDocument/didOpen', {
     textDocument = {
       version = lsp.util.buf_versions[bufnr],
-      uri = vim.uri_from_bufnr(bufnr),
+      uri = vim.uri.from_buf(bufnr),
       languageId = self:_get_language_id(bufnr),
       text = lsp._buf_get_full_text(bufnr),
     },
diff --git a/runtime/lua/vim/lsp/diagnostic.lua b/runtime/lua/vim/lsp/diagnostic.lua
index 7e2bba393a..8da7664cd3 100644
--- a/runtime/lua/vim/lsp/diagnostic.lua
+++ b/runtime/lua/vim/lsp/diagnostic.lua
@@ -245,7 +245,7 @@ end
 --- @param is_pull? boolean
 --- @param pull_id? string
 local function handle_diagnostics(uri, client_id, diagnostics, is_pull, pull_id)
-  local fname = vim.uri_to_fname(uri)
+  local fname = vim.uri.to_fname(uri)
 
   if #diagnostics == 0 and vim.fn.bufexists(fname) == 0 then
     return
@@ -327,7 +327,7 @@ function M.on_diagnostic(error, result, ctx)
     -- Create a new client state if it doesn't exist for the related document. This will not enable
     -- diagnostic pulling by itself, but will allow previous result IDs to be passed correctly the
     -- next time this buffer's diagnostics are pulled.
-    local related_bufnr = vim.uri_to_bufnr(uri)
+    local related_bufnr = vim.uri.to_buf(uri)
     local related_diagnostics = Diagnostics.active[related_bufnr] or Diagnostics:new(related_bufnr)
     local related_state = related_diagnostics.client_state[client_id]
     if not related_state then
@@ -470,7 +470,7 @@ local function previous_result_ids(client_id, identifier)
       local result_id = state.result_id[key]
       if result_id then
         results[#results + 1] = {
-          uri = vim.uri_from_bufnr(bufnr),
+          uri = vim.uri.from_buf(bufnr),
           value = result_id,
         }
       end
@@ -503,7 +503,7 @@ function M._workspace_diagnostics(opts)
       ---@type lsp.WorkspaceDiagnosticParams
       local params = ctx.params
       for _, report in ipairs(result.items) do
-        local bufnr = vim.uri_to_bufnr(report.uri)
+        local bufnr = vim.uri.to_buf(report.uri)
 
         -- Start tracking the buffer (but don't send "textDocument/diagnostic" requests for it).
         local provider = Diagnostics.active[bufnr] or Diagnostics:new(bufnr)
diff --git a/runtime/lua/vim/lsp/document_color.lua b/runtime/lua/vim/lsp/document_color.lua
index e4a455bb4a..a15dc5f356 100644
--- a/runtime/lua/vim/lsp/document_color.lua
+++ b/runtime/lua/vim/lsp/document_color.lua
@@ -319,7 +319,7 @@ function M.color_presentation()
     return
   end
 
-  local uri = vim.uri_from_bufnr(bufnr)
+  local uri = vim.uri.from_buf(bufnr)
   local client = assert(lsp.get_client_by_id(client_id))
 
   --- @type lsp.ColorPresentationParams
diff --git a/runtime/lua/vim/lsp/handlers.lua b/runtime/lua/vim/lsp/handlers.lua
index a3aeb3a5ba..d006cf678c 100644
--- a/runtime/lua/vim/lsp/handlers.lua
+++ b/runtime/lua/vim/lsp/handlers.lua
@@ -315,7 +315,7 @@ RCS['textDocument/documentSymbol'] = response_to_list(
   util.symbols_to_items,
   'document symbols',
   function(ctx)
-    local fname = vim.fn.fnamemodify(vim.uri_to_fname(ctx.params.textDocument.uri), ':.')
+    local fname = vim.fn.fnamemodify(vim.uri.to_fname(ctx.params.textDocument.uri), ':.')
     return string.format('Symbols in %s', fname)
   end
 )
@@ -539,7 +539,7 @@ local function make_call_hierarchy_handler(direction)
       local filename = nil
       local bufnr = nil
       if direction == 'from' then
-        filename = vim.uri_to_fname(call_hierarchy_item.uri)
+        filename = vim.uri.to_fname(call_hierarchy_item.uri)
       else
         bufnr = ctx.bufnr
       end
@@ -589,7 +589,7 @@ local function make_type_hierarchy_handler()
       local pos =
         vim.pos.lsp(assert(ctx.bufnr), type_hierarchy_item.range.start, client.offset_encoding)
       table.insert(items, {
-        filename = vim.uri_to_fname(type_hierarchy_item.uri),
+        filename = vim.uri.to_fname(type_hierarchy_item.uri),
         text = format_item(type_hierarchy_item),
         lnum = pos.row + 1,
         col = pos.col + 1,
diff --git a/runtime/lua/vim/lsp/tagfunc.lua b/runtime/lua/vim/lsp/tagfunc.lua
index 35c1031b41..ea3f8a38e8 100644
--- a/runtime/lua/vim/lsp/tagfunc.lua
+++ b/runtime/lua/vim/lsp/tagfunc.lua
@@ -8,13 +8,13 @@ local util = lsp.util
 ---@param position_encoding 'utf-8'|'utf-16'|'utf-32'
 ---@return {name: string, filename: string, cmd: string, kind?: string}
 local function mk_tag_item(name, range, uri, position_encoding)
-  local bufnr = vim.uri_to_bufnr(uri)
+  local bufnr = vim.uri.to_buf(uri)
   -- This is get_line_byte_from_position is 0-indexed, call cursor expects a 1-indexed position
   local pos = vim.pos.lsp(bufnr, range.start, position_encoding)
   local byte = pos.col + 1
   return {
     name = name,
-    filename = vim.uri_to_fname(uri),
+    filename = vim.uri.to_fname(uri),
     cmd = string.format([[/\%%%dl\%%%dc/]], range.start.line + 1, byte),
   }
 end
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index d35a3b2c18..fb48bab6f4 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -402,7 +402,7 @@ function M.apply_text_document_edit(
   validate('position_encoding', position_encoding, 'string')
 
   local text_document = text_document_edit.textDocument
-  local bufnr = vim.uri_to_bufnr(text_document.uri)
+  local bufnr = vim.uri.to_buf(text_document.uri)
 
   -- `VersionedTextDocumentIdentifier`s version may be null
   --  https://microsoft.github.io/language-server-protocol/specification#versionedTextDocumentIdentifier
@@ -557,7 +557,7 @@ end
 local function create_file(change)
   local opts = change.options or {}
   -- from spec: Overwrite wins over `ignoreIfExists`
-  local fname = vim.uri_to_fname(change.uri)
+  local fname = vim.uri.to_fname(change.uri)
   if not opts.ignoreIfExists or opts.overwrite then
     vim.fn.mkdir(vim.fs.dirname(fname), 'p')
     local file = io.open(fname, 'w')
@@ -571,7 +571,7 @@ end
 --- @param change lsp.DeleteFile
 local function delete_file(change)
   local opts = change.options or {}
-  local fname = vim.uri_to_fname(change.uri)
+  local fname = vim.uri.to_fname(change.uri)
   local bufnr = vim.fn.bufadd(fname)
   vim.fs.rm(fname, {
     force = opts.ignoreIfNotExists,
@@ -593,7 +593,7 @@ function M.apply_workspace_edit(workspace_edit, position_encoding)
     for idx, change in ipairs(workspace_edit.documentChanges) do
       if change.kind == 'rename' then
         local options = change.options --[[@as vim.lsp.util.rename.Opts]]
-        M.rename(vim.uri_to_fname(change.oldUri), vim.uri_to_fname(change.newUri), options)
+        M.rename(vim.uri.to_fname(change.oldUri), vim.uri.to_fname(change.newUri), options)
       elseif change.kind == 'create' then
         create_file(change)
       elseif change.kind == 'delete' then
@@ -601,7 +601,7 @@ function M.apply_workspace_edit(workspace_edit, position_encoding)
       elseif change.kind then --- @diagnostic disable-line:undefined-field
         error(string.format('Unsupported change: %q', vim.inspect(change)))
       else
-        local bufnr = vim.uri_to_bufnr(change.textDocument.uri)
+        local bufnr = vim.uri.to_buf(change.textDocument.uri)
         M.apply_text_document_edit(change, idx, position_encoding, workspace_edit.changeAnnotations)
         -- avoid triggering OptionSet
         if not vim.bo[bufnr].buflisted then
@@ -618,7 +618,7 @@ function M.apply_workspace_edit(workspace_edit, position_encoding)
   end
 
   for uri, changes in pairs(all_changes) do
-    local bufnr = vim.uri_to_bufnr(uri)
+    local bufnr = vim.uri.to_buf(uri)
     M.apply_text_edits(changes, bufnr, position_encoding, workspace_edit.changeAnnotations)
     -- avoid triggering OptionSet
     if not vim.bo[bufnr].buflisted then
@@ -925,7 +925,7 @@ end
 --- @param opts? vim.lsp.util.show_document.Opts
 --- @return boolean
 function M._show_document(uri, range, position_encoding, opts)
-  local bufnr = vim.uri_to_bufnr(uri)
+  local bufnr = vim.uri.to_buf(uri)
 
   -- Return early if the buffer fails to load, to avoid partial setup.
   local loaded, err = pcall(vim.fn.bufload, bufnr)
@@ -995,7 +995,7 @@ function M.preview_location(location, opts)
   if uri == nil then
     return
   end
-  local bufnr = vim.uri_to_bufnr(uri)
+  local bufnr = vim.uri.to_buf(uri)
   if not api.nvim_buf_is_loaded(bufnr) then
     vim.fn.bufload(bufnr)
   end
@@ -1802,7 +1802,7 @@ function M.locations_to_items(locations, position_encoding)
 
   for uri, rows in vim.spairs(grouped) do
     table.sort(rows, position_sort)
-    local filename = vim.uri_to_fname(uri)
+    local filename = vim.uri.to_fname(uri)
 
     local line_numbers = {}
     for _, temp in ipairs(rows) do
@@ -1813,7 +1813,7 @@ function M.locations_to_items(locations, position_encoding)
     end
 
     -- get all the lines for this uri
-    local lines = get_lines(vim.uri_to_bufnr(uri), line_numbers)
+    local lines = get_lines(vim.uri.to_buf(uri), line_numbers)
 
     for _, temp in ipairs(rows) do
       local pos = temp.start
@@ -1857,7 +1857,7 @@ function M.symbols_to_items(symbols, bufnr, position_encoding)
 
     if symbol.location then
       --- @cast symbol lsp.SymbolInformation
-      filename = vim.uri_to_fname(symbol.location.uri)
+      filename = vim.uri.to_fname(symbol.location.uri)
       range = vim.range.lsp(bufnr, symbol.location.range, position_encoding)
     elseif symbol.selectionRange then
       --- @cast symbol lsp.DocumentSymbol
@@ -1962,7 +1962,7 @@ end
 ---@return lsp.TextDocumentIdentifier
 ---@see https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocumentIdentifier
 function M.make_text_document_params(bufnr)
-  return { uri = vim.uri_from_bufnr(bufnr or 0) }
+  return { uri = vim.uri.from_buf(bufnr or 0) }
 end
 
 --- Create the workspace params
@@ -1997,7 +1997,7 @@ function M.make_formatting_params(options)
     insertSpaces = vim.bo.expandtab,
   }) --[[@as lsp.FormattingOptions]]
   return {
-    textDocument = { uri = vim.uri_from_bufnr(0) },
+    textDocument = { uri = vim.uri.from_buf(0) },
     options = options,
   }
 end
diff --git a/runtime/lua/vim/pack/_lsp.lua b/runtime/lua/vim/pack/_lsp.lua
index e42149b7bb..1e702b05e0 100644
--- a/runtime/lua/vim/pack/_lsp.lua
+++ b/runtime/lua/vim/pack/_lsp.lua
@@ -111,7 +111,7 @@ local function match_link(line, pattern, link_type, lnum, src)
     ---@diagnostic disable-next-line: param-type-mismatch
     target = require('vim._core.util').get_forge_url(src, match, link_type)
   elseif link_type == 'path' then
-    target = vim.uri_from_fname(match)
+    target = vim.uri.from_fname(match)
   end
 
   if target == nil then
diff --git a/runtime/lua/vim/pos/_util.lua b/runtime/lua/vim/pos/_util.lua
index be43d2b83e..8123c8fd58 100644
--- a/runtime/lua/vim/pos/_util.lua
+++ b/runtime/lua/vim/pos/_util.lua
@@ -83,7 +83,7 @@ function M.get_lines(buf, rows)
   -- Load the buffer if this is not a file URI.
   -- Custom language server protocol extensions can result in servers sending
   -- URIs with custom schemes. Plugins are able to load these via `BufReadCmd` autocmds.
-  if not vim.startswith(vim.uri_from_bufnr(buf), 'file://') then
+  if not vim.startswith(vim.uri.from_buf(buf), 'file://') then
     vim.fn.bufload(buf)
     return buf_lines()
   end
diff --git a/runtime/lua/vim/ui.lua b/runtime/lua/vim/ui.lua
index 6d98b08dc4..8fe7af3c74 100644
--- a/runtime/lua/vim/ui.lua
+++ b/runtime/lua/vim/ui.lua
@@ -182,8 +182,7 @@ end
 ---@see |vim.system()|
 function M.open(path, opt)
   vim.validate('path', path, 'string')
-  local is_uri = path:match('%w+:')
-  if not is_uri then
+  if not vim.uri.parse(path) then
     path = vim.fs.normalize(path)
   end
 
@@ -202,8 +201,9 @@ function M.open(path, opt)
     if open_cmd[1] == 'xdg-open' then
       job_opt.stdout = false
       job_opt.stderr = false
-    elseif open_cmd[1] == 'cmd.exe' and is_uri then
-      path = path:gsub('([&|<>^%%!])', '^%1') -- Escape cmd.exe special chars. #41337
+    elseif open_cmd[1] == 'cmd.exe' and not path:find('[%s"]') then
+      -- Escape cmd.exe special chars, unless libuv quotes the arg (it has whitespace or '"').
+      path = path:gsub('([&|<>^%%!])', '^%1')
     end
     cmd = vim.list_extend(open_cmd, { path })
   end
@@ -260,7 +260,7 @@ local get_lsp_urls = function(bufnr)
         if document_link.target and range:has(position) then
           local target = document_link.target ---@type string
           if vim.startswith(target, 'file://') then
-            target = vim.uri_to_fname(target)
+            target = vim.uri.to_fname(target)
           end
           table.insert(urls, target)
         end
diff --git a/runtime/lua/vim/uri.lua b/runtime/lua/vim/uri.lua
index bfc0c342cb..2bf404f11d 100644
--- a/runtime/lua/vim/uri.lua
+++ b/runtime/lua/vim/uri.lua
@@ -1,23 +1,19 @@
--- TODO: This is implemented only for files currently.
 -- https://tools.ietf.org/html/rfc3986
 -- https://tools.ietf.org/html/rfc2732
 -- https://tools.ietf.org/html/rfc2396
+-- https://tools.ietf.org/html/rfc8089
 
 local M = {}
 local sbyte = string.byte
 local schar = string.char
 local tohex = require('bit').tohex
-local URI_SCHEME_PATTERN = '^([a-zA-Z]+[a-zA-Z0-9.+-]*):.*'
-local WINDOWS_URI_SCHEME_PATTERN = '^([a-zA-Z]+[a-zA-Z0-9.+-]*):[a-zA-Z]:.*'
+local iswin = package.config:sub(1, 1) == '\\'
 local PATTERNS = {
-  -- RFC 2396
-  -- https://tools.ietf.org/html/rfc2396#section-2.2
+  -- RFC 2396 https://tools.ietf.org/html/rfc2396#section-2.3
   rfc2396 = "^A-Za-z0-9%-_.!~*'()",
-  -- RFC 2732
-  -- https://tools.ietf.org/html/rfc2732
+  -- RFC 2732 https://tools.ietf.org/html/rfc2732
   rfc2732 = "^A-Za-z0-9%-_.!~*'()%[%]",
-  -- RFC 3986
-  -- https://tools.ietf.org/html/rfc3986#section-2.2
+  -- RFC 3986 https://tools.ietf.org/html/rfc3986#section-3.3
   rfc3986 = "^A-Za-z0-9%-._~!$&'()*+,;=:@/",
 }
 
@@ -34,97 +30,189 @@ local function percent_encode_char(char)
   return '%' .. tohex(sbyte(char), 2)
 end
 
+local uri_mt = {
+  --- @param uri vim.Uri
+  --- @return string
+  __tostring = function(uri)
+    return ('%s:%s%s%s%s'):format(
+      uri.scheme,
+      uri.authority and ('//%s'):format(uri.authority) or '',
+      uri.path,
+      uri.query and ('?%s'):format(uri.query) or '',
+      uri.fragment and ('#%s'):format(uri.fragment) or ''
+    )
+  end,
+}
+
+--- @class vim.Uri
+---
+--- Scheme, e.g. "https".
+--- @field scheme string
+---
+--- Authority (after "//"), e.g. "user@example.com:8080". Empty for "file:///a", nil for "file:/a".
+--- @field authority? string
+---
+--- Path, e.g. "/a/b". Empty for "https://example.com".
+--- @field path string
+---
+--- Query (after "?"), e.g. "q=1".
+--- @field query? string
+---
+--- Fragment (after "#"), e.g. "section".
+--- @field fragment? string
+
+--- Parses a URI into its RFC 3986 components, without decoding them. Unlike RFC 3986, a one-letter
+--- scheme is a drive letter, so `C:/a` is not a URI.
+---
+--- Example:
+---
+--- ```lua
+--- vim.uri.parse('https://example.com/a%20b?q=1#section')
+--- --> { scheme = 'https', authority = 'example.com', path = '/a%20b', query = 'q=1', fragment = 'section' }
+--- vim.uri.parse('/a/b') --> nil
+--- vim.uri.parse('C:/a') --> nil
+--- tostring(vim.uri.parse('file:///a?b')) --> 'file:///a?b'
+--- ```
+---
+---@since 15
 ---@param uri string
----@return boolean
-local function is_windows_file_uri(uri)
-  return uri:match('^file:/+[a-zA-Z]:') ~= nil
+---@return vim.Uri? # URI components, or nil if `uri` has no scheme.
+function M.parse(uri)
+  -- Requires 2+ chars, so drive letters ("C:/a") are not schemes.
+  local scheme = uri:match('^(%a[%w+.-]+):')
+  if not scheme then
+    return nil
+  end
+  local rest = uri:sub(#scheme + 2)
+  local fragment_i = rest:find('#', 1, true)
+  local fragment = fragment_i and rest:sub(fragment_i + 1) or nil
+  rest = rest:sub(1, (fragment_i or 0) - 1)
+  local query_i = rest:find('?', 1, true)
+  local query = query_i and rest:sub(query_i + 1) or nil
+  rest = rest:sub(1, (query_i or 0) - 1)
+  local authority, path = rest:match('^//([^/]*)(.*)$') --- @type string?, string?
+  return setmetatable({
+    scheme = scheme,
+    authority = authority,
+    path = path or rest,
+    query = query,
+    fragment = fragment,
+  }, uri_mt)
 end
 
----URI-encodes a string using percent escapes.
+---URI-encodes a string.
+---@since 15
 ---@param str string string to encode
 ---@param rfc "rfc2396" | "rfc2732" | "rfc3986" | nil
 ---@return string encoded string
-function M.uri_encode(str, rfc)
+function M.encode(str, rfc)
   local pattern = PATTERNS[rfc] or PATTERNS.rfc3986
   return (str:gsub('([' .. pattern .. '])', percent_encode_char)) -- clamped to 1 retval with ()
 end
 
----URI-decodes a string containing percent escapes.
+---Decodes a URI-encoded string.
+---@since 15
 ---@param str string string to decode
 ---@return string decoded string
-function M.uri_decode(str)
+function M.decode(str)
   return (str:gsub('%%([a-fA-F0-9][a-fA-F0-9])', hex_to_char)) -- clamped to 1 retval with ()
 end
 
----Gets a URI from a file path.
+---Gets a URI from a file path. Relative paths are resolved to |current-directory| (RFC 8089
+---disallows relative URIs).
+---
+---Example:
+---
+---```lua
+---vim.uri.from_fname('/a b/c#') --> 'file:///a%20b/c%23'
+---vim.uri.from_fname('C:\\a\\b') --> 'file:///C:/a/b'
+---vim.uri.from_fname('//server/share/a') --> 'file://server/share/a' (UNC)
+---vim.uri.from_fname('a') --> 'file:///home/user/a' (if CWD is "/home/user")
+---```
+---
+---@since 15
 ---@param path string Path to file
 ---@return string URI
-function M.uri_from_fname(path)
-  local volume_path, fname = path:match('^([a-zA-Z]:)(.*)') ---@type string?, string?
-  local is_windows = volume_path ~= nil
-  if is_windows then
-    assert(fname)
-    path = volume_path .. M.uri_encode((fname:gsub('\\', '/')))
-  else
-    path = M.uri_encode(path)
+function M.from_fname(path)
+  if iswin or path:find('^%a:') then
+    path = path:gsub('\\', '/') ---@type string
   end
-  local uri_parts = { 'file://' }
-  if is_windows then
-    table.insert(uri_parts, '/')
+  if path ~= '' and not path:find('^/') and not path:find('^%a:') then
+    path = vim.fs.normalize(vim.fs.abspath(path, { plain = true }), { plain = true }) -- Force absolute, RFC 8089 disallows relative.
   end
-  table.insert(uri_parts, path)
-  return table.concat(uri_parts)
+  local host = path:match('^//([^/]+)') ---@type string?
+  if host then -- UNC path.
+    return ('file://%s%s'):format(M.encode(host), M.encode(path:sub(#host + 3)))
+  end
+  local drive = path:match('^%a:') ---@type string?
+  if drive then -- Windows drive letter.
+    return ('file:///%s%s'):format(drive, M.encode(path:sub(3)))
+  end
+  return ('file://%s'):format(M.encode(path))
 end
 
----Gets a URI from a bufnr.
+---Gets a URI from a buffer.
+---@since 15
 ---@param buf integer
 ---@return string URI
-function M.uri_from_bufnr(buf)
+function M.from_buf(buf)
   local fname = vim.api.nvim_buf_get_name(buf)
-  local volume_path = fname:match('^([a-zA-Z]:).*')
-  local is_windows = volume_path ~= nil
-  local scheme ---@type string?
-  if is_windows then
-    fname = fname:gsub('\\', '/')
-    scheme = fname:match(WINDOWS_URI_SCHEME_PATTERN)
-  else
-    scheme = fname:match(URI_SCHEME_PATTERN)
-  end
-  if scheme then
+  if M.parse(fname) then
     return fname
-  else
-    return M.uri_from_fname(fname)
   end
+  return M.from_fname(fname)
 end
 
----Gets a filename from a URI.
+---Gets a filename from a URI. Drops the query and fragment, so "?" and "#" in a filename must be
+---percent-encoded.
+---
+---Example:
+---
+---```lua
+---vim.uri.to_fname('file:///a%3Fb?c#d') --> '/a?b'
+---vim.uri.to_fname('file:///C:/a/b') --> 'C:/a/b'
+---vim.uri.to_fname('file://server/share/a') --> '//server/share/a'
+---vim.uri.to_fname('jdt://a/b') --> 'jdt://a/b'
+---```
+---
+---@since 15
 ---@param uri string
 ---@return string filename or unchanged URI for non-file URIs
-function M.uri_to_fname(uri)
-  local scheme = uri:match(URI_SCHEME_PATTERN) or error('URI must contain a scheme: ' .. uri)
-  if scheme ~= 'file' then
+function M.to_fname(uri)
+  local parts = M.parse(uri)
+  if not parts and uri:find('^%a:') then -- Drive letter: already a filename.
     return uri
   end
-  local fragment_index = uri:find('#')
-  if fragment_index ~= nil then
-    uri = uri:sub(1, fragment_index - 1)
+  parts = parts or error(('URI must contain a scheme: %s'):format(uri))
+  if parts.scheme:lower() ~= 'file' then
+    return uri
   end
-  uri = M.uri_decode(uri)
-  --TODO improve this.
-  if is_windows_file_uri(uri) then
-    uri = uri:gsub('^file:/+', ''):gsub('/', '\\') --- @type string
-  else
-    uri = uri:gsub('^file:/+', '/') ---@type string
+  local host = M.decode(parts.authority or '')
+  local path = M.decode(parts.path)
+  if host:find('^%a:') then
+    -- Drive letter, not a host (like WHATWG URL): "file://C:/a" => "C:/a".
+    host, path = '', ('%s%s'):format(host, path)
   end
-  return uri
+  -- Collapses leading slashes: "file:a" => "/a", "file:////a" => "/a".
+  -- TODO(justinmk): Error on a relative path ("file:a"), like Rust `Url::to_file_path()`, unless
+  -- LSP servers send those?
+  path = path:gsub('^/*', '/') ---@type string
+  -- TODO: On Windows, accessing "//host/…" connects to the host (and may send NTLM credentials).
+  -- If users report it, allowlist hosts via a new option (like VS Code "security.allowedUNCHosts").
+  if host ~= '' and host:lower() ~= 'localhost' then -- UNC path.
+    return ('//%s%s'):format(host, path)
+  end
+  -- Drive letter: "/C:/a" => "C:/a".
+  return path:match('^/(%a:.*)$') or path
 end
 
 ---Gets the buffer for a uri.
 ---Creates a new unloaded buffer if no buffer for the uri already exists.
+---@since 15
 ---@param uri string
----@return integer bufnr
-function M.uri_to_bufnr(uri)
-  return vim.fn.bufadd(M.uri_to_fname(uri))
+---@return integer buf
+function M.to_buf(uri)
+  return vim.fn.bufadd(M.to_fname(uri))
 end
 
 return M
diff --git a/runtime/plugin/zip.lua b/runtime/plugin/zip.lua
index dc3f09c9c9..07f8fbb147 100644
--- a/runtime/plugin/zip.lua
+++ b/runtime/plugin/zip.lua
@@ -104,7 +104,7 @@ api.nvim_create_autocmd('BufReadCmd', {
     if legacy_loaded() then
       return true
     end
-    if ev.match:match('^%a[%w+.-]*://') then
+    if vim._core.path_is_url(ev.match) then
       return
     end
     require('nvim.zip').browse(ev.buf, ev.match)
diff --git a/src/gen/gen_steps.zig b/src/gen/gen_steps.zig
index f1a7758156..0f39365274 100644
--- a/src/gen/gen_steps.zig
+++ b/src/gen/gen_steps.zig
@@ -81,6 +81,7 @@ pub fn nvim_gen_sources(
             "loader",
             "text",
             "tty",
+            "uri",
         };
         for (names) |n| {
             gen_step.addFileArg(b.path(b.fmt("runtime/lua/vim/{s}.lua", .{n})));
diff --git a/src/gen/gen_vimdoc.lua b/src/gen/gen_vimdoc.lua
index 87523c3034..aa1cf1448d 100755
--- a/src/gen/gen_vimdoc.lua
+++ b/src/gen/gen_vimdoc.lua
@@ -243,7 +243,7 @@ local config = {
       'runtime/lua/vim/version.lua',
     },
     fn_xform = function(fun)
-      if contains(fun.module, { 'vim.uri', 'vim._core.shared', 'vim._core.editor' }) then
+      if contains(fun.module, { 'vim._core.shared', 'vim._core.editor' }) then
         fun.module = 'vim'
       end
 
diff --git a/src/gen/lint.lua b/src/gen/lint.lua
index 1c70091b5f..7f0c3c38b8 100644
--- a/src/gen/lint.lua
+++ b/src/gen/lint.lua
@@ -59,10 +59,6 @@ local legacy_names = {
     nvim_list_uis = true,
     nvim_list_wins = true,
   },
-  ['runtime/lua/vim/uri.lua'] = {
-    uri_from_bufnr = true,
-    uri_to_bufnr = true,
-  },
   ['runtime/lua/vim/_core/shared.lua'] = {
     _ensure_list = true,
     _list_insert = true,
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index d4bf2f0487..96a53bebf5 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -353,6 +353,7 @@ set(LUA_KEYMAP_MODULE_SOURCE ${NVIM_RUNTIME_DIR}/lua/vim/keymap.lua)
 set(LUA_LOADER_MODULE_SOURCE ${NVIM_RUNTIME_DIR}/lua/vim/loader.lua)
 set(LUA_TEXT_MODULE_SOURCE ${NVIM_RUNTIME_DIR}/lua/vim/text.lua)
 set(LUA_TTY_MODULE_SOURCE ${NVIM_RUNTIME_DIR}/lua/vim/tty.lua)
+set(LUA_URI_MODULE_SOURCE ${NVIM_RUNTIME_DIR}/lua/vim/uri.lua)
 
 # Find all Lua modules in the _core/ directory.
 file(GLOB LUA_CORE_MODULE_SOURCES ${NVIM_RUNTIME_DIR}/lua/vim/_core/*.lua)
@@ -655,6 +656,7 @@ add_custom_command(
       ${LUA_LOADER_MODULE_SOURCE} "vim.loader"
       ${LUA_TEXT_MODULE_SOURCE} "vim.text"
       ${LUA_TTY_MODULE_SOURCE} "vim.tty"
+      ${LUA_URI_MODULE_SOURCE} "vim.uri"
       ${LUA_CORE_COMMAND_ARGS}
   DEPENDS
     ${CHAR_BLOB_GENERATOR}
@@ -667,6 +669,7 @@ add_custom_command(
     ${LUA_LOADER_MODULE_SOURCE}
     ${LUA_TEXT_MODULE_SOURCE}
     ${LUA_TTY_MODULE_SOURCE}
+    ${LUA_URI_MODULE_SOURCE}
     ${LUA_CORE_MODULE_SOURCES}
   VERBATIM
 )
diff --git a/src/nvim/lua/stdlib.c b/src/nvim/lua/stdlib.c
index f1b49e9fd7..4e3ba95ac3 100644
--- a/src/nvim/lua/stdlib.c
+++ b/src/nvim/lua/stdlib.c
@@ -43,6 +43,7 @@
 #include "nvim/memline.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
+#include "nvim/path.h"
 #include "nvim/pos_defs.h"
 #include "nvim/regexp.h"
 #include "nvim/regexp_defs.h"
@@ -466,6 +467,13 @@ int nlua_getvar(lua_State *lstate)
   return 1;
 }
 
+/// Checks if a path is a URL. See path_with_url().
+static int nlua_path_is_url(lua_State *const lstate) FUNC_ATTR_NONNULL_ALL
+{
+  lua_pushboolean(lstate, path_with_url(luaL_checkstring(lstate, 1)));
+  return 1;
+}
+
 /// Compare two strings, ignoring case
 ///
 /// Expects two values on the stack: compared strings. Returns one of the
@@ -844,6 +852,12 @@ void nlua_state_add_stdlib(lua_State *const lstate, bool is_thread)
   lua_cjson_new(lstate);
   lua_setfield(lstate, -2, "json");
 
+  // vim._core.path_is_url
+  lua_getfield(lstate, -1, "_core");
+  lua_pushcfunction(lstate, &nlua_path_is_url);
+  lua_setfield(lstate, -2, "path_is_url");
+  lua_pop(lstate, 1);
+
 #ifdef NVIM_VENDOR_BIT
   // if building with puc lua, use internal fallback for require'bit'
   int top = lua_gettop(lstate);
diff --git a/src/nvim/path.c b/src/nvim/path.c
index fdf1e7e7d4..f67a1504ca 100644
--- a/src/nvim/path.c
+++ b/src/nvim/path.c
@@ -36,11 +36,6 @@
 #include "nvim/strings.h"
 #include "nvim/vim_defs.h"
 
-enum {
-  URL_SLASH = 1,      // path_is_url() has found ":/"
-  URL_BACKSLASH = 2,  // path_is_url() has found ":\\"
-};
-
 #ifdef gen_expand_wildcards
 # undef gen_expand_wildcards
 #endif
@@ -1690,38 +1685,31 @@ bool path_has_drive_letter(const char *p, size_t path_len)
          && (path_len == 2 || ((p[2] == '/') | (p[2] == '\\') | (p[2] == '?') | (p[2] == '#')));
 }
 
-// Check if the ":/" of a URL is at the pointer, return URL_SLASH.
-// Also check for ":\\", which MS Internet Explorer accepts, return
-// URL_BACKSLASH.
-int path_is_url(const char *p)
+/// Checks if the ":/" of a URL is at the pointer.
+bool path_is_url(const char *p)
   FUNC_ATTR_NONNULL_ALL
 {
-  // In the spec ':' is enough to recognize a scheme
-  // https://url.spec.whatwg.org/#scheme-state
-  if (strncmp(p, ":/", 2) == 0) {
-    return URL_SLASH;
-  } else if (strncmp(p, ":\\\\", 3) == 0) {
-    return URL_BACKSLASH;
-  }
-  return 0;
+  return strncmp(p, ":/", 2) == 0;
 }
 
-/// Check if "fname" starts with "name:/" or "name:\".
+/// Checks if `fname` is a URL (not a filepath).
+///
+/// - "deno:/a" and "fugitive:///a" are URLs
+/// - "C:/a" (drive letter) and "mailto:a" are NOT.
 ///
 /// @param  fname         is the filename to test
-/// @return URL_SLASH for "name:/", URL_BACKSLASH for "name:\", zero otherwise.
-int path_with_url(const char *fname)
+bool path_with_url(const char *fname)
   FUNC_ATTR_NONNULL_ALL
 {
   const char *p;
 
   // first character must be alpha
   if (!ASCII_ISALPHA(*fname)) {
-    return 0;
+    return false;
   }
 
   if (path_has_drive_letter(fname, strlen(fname))) {
-    return 0;
+    return false;
   }
 
   // check body: (alpha, digit, '+', '-', '.') following RFC3986
@@ -1729,10 +1717,10 @@ int path_with_url(const char *fname)
 
   // check last char is not '+', '-', or '.'
   if ((p[-1] == '+') || (p[-1] == '-') || (p[-1] == '.')) {
-    return 0;
+    return false;
   }
 
-  // ":/" or ":\\" must follow
+  // ":/" must follow
   return path_is_url(p);
 }
 
diff --git a/test/functional/core/main_spec.lua b/test/functional/core/main_spec.lua
index 075fc24a5d..99ca1dea23 100644
--- a/test/functional/core/main_spec.lua
+++ b/test/functional/core/main_spec.lua
@@ -233,6 +233,7 @@ describe('vim._core', function()
       'vim.loader',
       'vim.text',
       'vim.tty',
+      'vim.uri',
     }
     if n.exec_lua [[return not not _G.jit]] then
       expected = vim.list_extend({
diff --git a/test/functional/lua/diagnostic_spec.lua b/test/functional/lua/diagnostic_spec.lua
index 5c85376542..f6b1ae84d5 100644
--- a/test/functional/lua/diagnostic_spec.lua
+++ b/test/functional/lua/diagnostic_spec.lua
@@ -3688,7 +3688,7 @@ describe('vim.diagnostic', function()
 
       -- Populate the related info buffer.
       exec_lua(function()
-        local fake_bufnr = vim.uri_to_bufnr(related_info_uri)
+        local fake_bufnr = vim.uri.to_buf(related_info_uri)
         vim.fn.bufload(fake_bufnr)
         vim.api.nvim_buf_set_lines(fake_bufnr, 0, 1, false, {
           'O, the Pelican,',
diff --git a/test/functional/lua/filetype_spec.lua b/test/functional/lua/filetype_spec.lua
index fdc6e8c757..4a4505878d 100644
--- a/test/functional/lua/filetype_spec.lua
+++ b/test/functional/lua/filetype_spec.lua
@@ -84,16 +84,33 @@ describe('vim.filetype', function()
     )
   end)
 
-  it('matches URI buffer patterns ending in slash', function()
+  it('matches URI buffer names as-is #42598', function()
     eq(
-      'example',
+      { 'example', 'myft', 'fugitive:///repo/a.sql', 'deno:/https/deno.land/a.sql' },
       exec_lua(function()
         vim.filetype.add({
+          filename = {
+            ['myscheme://project/foo'] = 'myft',
+          },
           pattern = {
             ['example://.*'] = 'example',
+            -- Detects the path passed to filetype functions as the filetype.
+            ['.*%.sql'] = function(path)
+              return path
+            end,
           },
         })
-        return vim.filetype.match({ filename = 'example:///tmp/example/' })
+        local names = {
+          'example:///tmp/example/',
+          'myscheme://project/foo',
+          'fugitive:///repo/a.sql',
+          'deno:/https/deno.land/a.sql',
+        }
+        local fts = {} ---@type string[]
+        for i, name in ipairs(names) do
+          fts[i] = vim.filetype.match({ filename = name })
+        end
+        return fts
       end)
     )
   end)
diff --git a/test/functional/lua/fs_spec.lua b/test/functional/lua/fs_spec.lua
index a6608ec278..625cd4df34 100644
--- a/test/functional/lua/fs_spec.lua
+++ b/test/functional/lua/fs_spec.lua
@@ -619,6 +619,18 @@ describe('vim.fs', function()
 
     it('works with a filename argument', function()
       eq(test_source_path, exec_lua([[return vim.fs.root(..., 'CMakePresets.json')]], nvim_prog))
+      eq_paths(
+        test_source_path,
+        exec_lua([[return vim.fs.root(vim.uri.from_fname(...), 'CMakePresets.json')]], nvim_prog)
+      )
+      -- Scheme is case-insensitive.
+      eq_paths(
+        test_source_path,
+        exec_lua(
+          [[return vim.fs.root(vim.uri.from_fname(...):gsub('^file:', 'FILE:'), 'CMakePresets.json')]],
+          nvim_prog
+        )
+      )
     end)
 
     it('works with a relative path', function()
@@ -642,11 +654,11 @@ describe('vim.fs', function()
       eq_paths(test_source_path, exec_lua([[return vim.fs.root(0, 'CMakePresets.json')]]))
     end)
 
-    it('returns CWD (absolute path) if no match is found', function()
+    it('returns CWD (absolute path) for a URL', function()
       assert(n.fn.isabsolutepath(test_source_path) == 1)
       eq_paths(
         test_source_path,
-        exec_lua([[return vim.fs.root('file://bogus', 'CMakePresets.json')]])
+        exec_lua([[return vim.fs.root('foo://bogus', 'CMakePresets.json')]])
       )
     end)
   end)
@@ -930,6 +942,13 @@ describe('vim.fs', function()
         eq('/foo/../.', vim.fs.abspath('/foo/../.'))
         eq('/foo/bar', vim.fs.abspath('/foo/bar'))
       end
+      eq('fugitive:///repo/.git//0/a', vim.fs.abspath('fugitive:///repo/.git//0/a'))
+      eq('deno:/https/deno.land/a', vim.fs.abspath('deno:/https/deno.land/a'))
+      -- Drive letter, not a URL scheme.
+      eq(
+        { false, false },
+        { vim._core.path_is_url([[C:\foo\bar]]), vim._core.path_is_url('C:/foo') }
+      )
     end)
 
     it('with `cwd`', function()
diff --git a/test/functional/lua/thread_spec.lua b/test/functional/lua/thread_spec.lua
index 814c1bb611..ac88fe1f81 100644
--- a/test/functional/lua/thread_spec.lua
+++ b/test/functional/lua/thread_spec.lua
@@ -8,10 +8,31 @@ local clear = n.clear
 local feed = n.feed
 local eq = t.eq
 local exec_lua = n.exec_lua
-local next_msg = n.next_msg
 local NIL = vim.NIL
 local pcall_err = t.pcall_err
 
+--- Calls `vim.*` functions in a thread. Returns the results as an mpack-encoded table.
+local vim_fns = [[
+  return vim.mpack.encode({
+    diff = vim.diff('Hello\n', 'Helli\n'),
+    is_thread = vim.is_thread(),
+    json = vim.json.decode(vim.json.encode({ 33, vim.NIL, 'text' })),
+    mpack = vim.mpack.decode(vim.mpack.encode({ 33, vim.NIL, 'text' })),
+    path_is_url = vim._core.path_is_url('deno:/a'),
+    uri = vim.uri.to_fname('file:///a') .. vim.uri_to_fname('file:///b'),
+    uv = vim.uv.version() >= 72961,
+  })
+]]
+local vim_fns_expected = {
+  diff = '@@ -1 +1 @@\n-Hello\n+Helli\n',
+  is_thread = true,
+  json = { 33, NIL, 'text' },
+  mpack = { 33, NIL, 'text' },
+  path_is_url = true,
+  uri = '/a/b',
+  uv = true,
+}
+
 describe('thread', function()
   local screen
 
@@ -119,150 +140,31 @@ describe('thread', function()
     end)
   end)
 
-  describe('vim.*', function()
-    before_each(function()
-      clear()
-      exec_lua [[
-        Thread_Test = {}
-
-        Thread_Test.entry_func = function(async, entry_str, args)
-          local decoded_args = vim.mpack.decode(args)
-          assert(loadstring(entry_str))(async, decoded_args)
-        end
-
-        function Thread_Test:do_test()
-          local async
-          local on_async = self.on_async
-          async = vim.uv.new_async(function(ret)
-            on_async(ret)
-            async:close()
-          end)
-          local thread =
-            vim.uv.new_thread(self.entry_func, async, self.entry_str, self.args)
-          vim.uv.thread_join(thread)
-        end
-
-        Thread_Test.new = function(entry, on_async, ...)
-          self = {}
-          setmetatable(self, {__index = Thread_Test})
-          self.args = vim.mpack.encode({...})
-          self.entry_str = string.dump(entry)
-          self.on_async = on_async
-          return self
-        end
-      ]]
-    end)
-
-    it('is_thread', function()
-      exec_lua [[
-        local entry = function(async)
-          async:send(vim.is_thread())
-        end
-        local on_async = function(ret)
-          vim.rpcnotify(1, 'result', ret)
-        end
-        local thread_test = Thread_Test.new(entry, on_async)
-        thread_test:do_test()
-      ]]
-
-      eq({ 'notification', 'result', { true } }, next_msg())
-    end)
-
-    it('uv', function()
-      exec_lua [[
-        local entry = function(async)
-          async:send(vim.uv.version())
-        end
-        local on_async = function(ret)
-          vim.rpcnotify(1, ret)
-        end
-        local thread_test = Thread_Test.new(entry, on_async)
-        thread_test:do_test()
-      ]]
-
-      local msg = next_msg()
-      eq('notification', msg[1])
-      assert(tonumber(msg[2]) >= 72961)
-    end)
-
-    it('mpack', function()
-      exec_lua [[
-        local entry = function(async)
-          async:send(vim.mpack.encode({33, vim.NIL, 'text'}))
-        end
-        local on_async = function(ret)
-          vim.rpcnotify(1, 'result', vim.mpack.decode(ret))
-        end
-        local thread_test = Thread_Test.new(entry, on_async)
-        thread_test:do_test()
-      ]]
-
-      eq({ 'notification', 'result', { { 33, NIL, 'text' } } }, next_msg())
-    end)
-
-    it('json', function()
-      exec_lua [[
-        local entry = function(async)
-        async:send(vim.json.encode({33, vim.NIL, 'text'}))
-        end
-        local on_async = function(ret)
-        vim.rpcnotify(1, 'result', vim.json.decode(ret))
-        end
-        local thread_test = Thread_Test.new(entry, on_async)
-        thread_test:do_test()
-      ]]
-
-      eq({ 'notification', 'result', { { 33, NIL, 'text' } } }, next_msg())
-    end)
-
-    it('diff', function()
-      exec_lua [[
-        local entry = function(async)
-          async:send(vim.diff('Hello\n', 'Helli\n'))
-        end
-        local on_async = function(ret)
-          vim.rpcnotify(1, 'result', ret)
-        end
-        local thread_test = Thread_Test.new(entry, on_async)
-        thread_test:do_test()
-      ]]
-
-      eq({
-        'notification',
-        'result',
-        {
-          table.concat({
-            '@@ -1 +1 @@',
-            '-Hello',
-            '+Helli',
-            '',
-          }, '\n'),
-        },
-      }, next_msg())
-    end)
+  it('vim.* functions', function()
+    eq(
+      vim_fns_expected,
+      exec_lua(function()
+        local result --- @type table?
+        local async = assert(vim.uv.new_async(function(ret)
+          result = vim.mpack.decode(ret)
+        end))
+        local thread = assert(vim.uv.new_thread(function(async_, code)
+          async_:send(assert(loadstring(code))())
+        end, async, vim_fns))
+        vim.uv.thread_join(thread)
+        vim.wait(2000, function()
+          return result ~= nil
+        end)
+        async:close()
+        return result
+      end)
+    )
   end)
 end)
 
 describe('threadpool', function()
   before_each(clear)
 
-  it('is_thread', function()
-    eq(false, exec_lua [[return vim.is_thread()]])
-
-    exec_lua [[
-      local work_fn = function()
-        return vim.is_thread()
-      end
-      local after_work_fn = function(ret)
-        vim.rpcnotify(1, 'result', ret)
-      end
-      local work = vim.uv.new_work(work_fn, after_work_fn)
-      work:queue()
-    ]]
-
-    eq({ 'notification', 'result', { true } }, next_msg())
-  end)
-
   it('with invalid argument', function()
     local status = pcall_err(
       exec_lua,
@@ -293,107 +195,23 @@ describe('threadpool', function()
     ]])
   end)
 
-  describe('vim.*', function()
-    before_each(function()
-      clear()
-      exec_lua [[
-        Threadpool_Test = {}
-
-        Threadpool_Test.work_fn = function(work_fn_str, args)
-          local decoded_args = vim.mpack.decode(args)
-          return assert(loadstring(work_fn_str))(decoded_args)
-        end
-
-        function Threadpool_Test:do_test()
-          local work =
-            vim.uv.new_work(self.work_fn, self.after_work)
-          work:queue(self.work_fn_str, self.args)
-        end
-
-        Threadpool_Test.new = function(work_fn, after_work, ...)
-          self = {}
-          setmetatable(self, {__index = Threadpool_Test})
-          self.args = vim.mpack.encode({...})
-          self.work_fn_str = string.dump(work_fn)
-          self.after_work = after_work
-          return self
-        end
-      ]]
-    end)
-
-    it('uv', function()
-      exec_lua [[
-        local work_fn = function()
-          return vim.uv.version()
-        end
-        local after_work_fn = function(ret)
-          vim.rpcnotify(1, ret)
-        end
-        local threadpool_test = Threadpool_Test.new(work_fn, after_work_fn)
-        threadpool_test:do_test()
-      ]]
-
-      local msg = next_msg()
-      eq('notification', msg[1])
-      assert(tonumber(msg[2]) >= 72961)
-    end)
-
-    it('mpack', function()
-      exec_lua [[
-        local work_fn = function()
-          local var = vim.mpack.encode({33, vim.NIL, 'text'})
-          return var
-        end
-        local after_work_fn = function(ret)
-          vim.rpcnotify(1, 'result', vim.mpack.decode(ret))
-        end
-        local threadpool_test = Threadpool_Test.new(work_fn, after_work_fn)
-        threadpool_test:do_test()
-      ]]
-
-      eq({ 'notification', 'result', { { 33, NIL, 'text' } } }, next_msg())
-    end)
-
-    it('json', function()
-      exec_lua [[
-        local work_fn = function()
-          local var = vim.json.encode({33, vim.NIL, 'text'})
-          return var
-        end
-        local after_work_fn = function(ret)
-          vim.rpcnotify(1, 'result', vim.json.decode(ret))
-        end
-        local threadpool_test = Threadpool_Test.new(work_fn, after_work_fn)
-        threadpool_test:do_test()
-      ]]
-
-      eq({ 'notification', 'result', { { 33, NIL, 'text' } } }, next_msg())
-    end)
-
-    it('work', function()
-      exec_lua [[
-        local work_fn = function()
-          return vim.diff('Hello\n', 'Helli\n')
-        end
-        local after_work_fn = function(ret)
-          vim.rpcnotify(1, 'result', ret)
-        end
-        local threadpool_test = Threadpool_Test.new(work_fn, after_work_fn)
-        threadpool_test:do_test()
-      ]]
-
-      eq({
-        'notification',
-        'result',
-        {
-          table.concat({
-            '@@ -1 +1 @@',
-            '-Hello',
-            '+Helli',
-            '',
-          }, '\n'),
-        },
-      }, next_msg())
-    end)
+  it('vim.* functions', function()
+    eq(false, exec_lua('return vim.is_thread()'))
+    eq(
+      vim_fns_expected,
+      exec_lua(function()
+        local result --- @type table?
+        local work = vim.uv.new_work(function(code)
+          return assert(loadstring(code))()
+        end, function(ret)
+          result = vim.mpack.decode(ret)
+        end)
+        work:queue(vim_fns)
+        vim.wait(2000, function()
+          return result ~= nil
+        end)
+        return result
+      end)
+    )
   end)
 end)
diff --git a/test/functional/lua/ui_spec.lua b/test/functional/lua/ui_spec.lua
index 6dd4bba060..3f68570054 100644
--- a/test/functional/lua/ui_spec.lua
+++ b/test/functional/lua/ui_spec.lua
@@ -129,9 +129,14 @@ describe('vim.ui', function()
       )
     end)
 
-    it('escapes cmd.exe metacharacters in URIs #41337', function()
+    it('escapes cmd.exe metacharacters #41337', function()
       eq(
-        { 'cmd.exe', '/c', 'start', '', 'https://example.com/?q=^&^|^<^>^^^%^!' },
+        {
+          { 'cmd.exe', '/c', 'start', '', 'https://example.com/?q=^&^|^<^>^^^%^!' },
+          { 'cmd.exe', '/c', 'start', '', 'C:/a^&b.pdf' },
+          -- Not escaped: libuv quotes it.
+          { 'cmd.exe', '/c', 'start', '', 'C:/a b&c.pdf' },
+        },
         exec_lua(function()
           vim.fn.has = function(feat)
             return feat == 'win32' and 1 or 0
@@ -145,8 +150,12 @@ describe('vim.ui', function()
               end,
             }
           end
-          vim.ui.open('https://example.com/?q=&|<>^%!')
-          return captured
+          local cmds = {} --- @type string[][]
+          for _, path in ipairs({ 'https://example.com/?q=&|<>^%!', 'C:/a&b.pdf', 'C:/a b&c.pdf' }) do
+            vim.ui.open(path)
+            cmds[#cmds + 1] = captured
+          end
+          return cmds
         end)
       )
     end)
@@ -172,6 +181,14 @@ describe('vim.ui', function()
           return cmd:wait()
         end, { n.testprg('printargs-test'), 'arg1' })
       )
+
+      -- Expands a path containing ":".
+      eq(
+        ('arg1=%s/a:b;'):format(vim.fs.normalize('~')),
+        exec_lua(function(opener)
+          return vim.ui.open('~/a:b', { cmd = { opener } }):wait().stdout
+        end, n.testprg('printargs-test'))
+      )
     end)
 
     it('can reuse opt.cmd without accumulating paths', function()
@@ -205,7 +222,7 @@ describe('vim.ui', function()
       local param = url:match('%?tag=(.*)')
       local tagname =
         n.api.nvim_buf_get_text(0, tag[2], tag[3], tag[4].end_row, tag[4].end_col, {})[1]
-      eq(vim.uri_encode(tagname), param)
+      eq(vim.uri.encode(tagname), param)
 
       -- non-nvim tags are ignored
       local buf = n.api.nvim_create_buf(false, false)
diff --git a/test/functional/lua/uri_spec.lua b/test/functional/lua/uri_spec.lua
index 9cd8936b17..1bc17222e3 100644
--- a/test/functional/lua/uri_spec.lua
+++ b/test/functional/lua/uri_spec.lua
@@ -9,203 +9,228 @@ local is_os = t.is_os
 local skip = t.skip
 local write_file = t.write_file
 
-describe('URI methods', function()
+describe('vim.uri', function()
   before_each(function()
     clear()
   end)
 
-  describe('file path to uri', function()
-    describe('encode Unix file path', function()
-      it('file path includes only ascii characters', function()
-        exec_lua("filepath = '/Foo/Bar/Baz.txt'")
+  describe('from_fname()', function()
+    it('Unix filepath', function()
+      exec_lua("filepath = '/Foo/Bar/Baz.txt'")
 
-        eq('file:///Foo/Bar/Baz.txt', exec_lua('return vim.uri_from_fname(filepath)'))
-      end)
+      eq('file:///Foo/Bar/Baz.txt', exec_lua('return vim.uri.from_fname(filepath)'))
+      -- Resolves a relative path.
+      eq(
+        exec_lua(function()
+          local cwd = assert(vim.uv.cwd())
+          return {
+            vim.uri.from_fname(cwd .. '/a.txt'),
+            vim.uri.from_fname(vim.fs.dirname(cwd) .. '/b'),
+          }
+        end),
+        exec_lua(function()
+          return { vim.uri.from_fname('a.txt'), vim.uri.from_fname('../b') }
+        end)
+      )
 
-      it('file path including white space', function()
-        exec_lua("filepath = '/Foo /Bar/Baz.txt'")
+      exec_lua("filepath = '/Foo /Bar/Baz.txt'")
+      eq('file:///Foo%20/Bar/Baz.txt', exec_lua('return vim.uri.from_fname(filepath)'))
 
-        eq('file:///Foo%20/Bar/Baz.txt', exec_lua('return vim.uri_from_fname(filepath)'))
-      end)
-
-      it('file path including Unicode characters', function()
-        exec_lua("filepath = '/xy/åäö/ɧ/汉语/↥/🤦/🦄/å/بِيَّ.txt'")
-
-        -- The URI encoding should be case-insensitive
-        eq(
-          'file:///xy/%c3%a5%c3%a4%c3%b6/%c9%a7/%e6%b1%89%e8%af%ad/%e2%86%a5/%f0%9f%a4%a6/%f0%9f%a6%84/a%cc%8a/%d8%a8%d9%90%d9%8a%d9%8e%d9%91.txt',
-          exec_lua('return vim.uri_from_fname(filepath)')
-        )
-      end)
+      exec_lua("filepath = '/xy/åäö/ɧ/汉语/↥/🤦/🦄/å/بِيَّ.txt'")
+      -- The URI encoding should be case-insensitive
+      eq(
+        'file:///xy/%c3%a5%c3%a4%c3%b6/%c9%a7/%e6%b1%89%e8%af%ad/%e2%86%a5/%f0%9f%a4%a6/%f0%9f%a6%84/a%cc%8a/%d8%a8%d9%90%d9%8a%d9%8e%d9%91.txt',
+        exec_lua('return vim.uri.from_fname(filepath)')
+      )
     end)
 
-    describe('encode Windows filepath', function()
-      it('file path includes only ascii characters', function()
-        exec_lua([[filepath = 'C:\\Foo\\Bar\\Baz.txt']])
+    it('Windows filepath', function()
+      exec_lua([[filepath = 'C:\\Foo\\Bar\\Baz.txt']])
+      eq('file:///C:/Foo/Bar/Baz.txt', exec_lua('return vim.uri.from_fname(filepath)'))
 
-        eq('file:///C:/Foo/Bar/Baz.txt', exec_lua('return vim.uri_from_fname(filepath)'))
-      end)
+      exec_lua([[filepath = 'C:\\Foo \\Bar\\Baz.txt']])
+      eq('file:///C:/Foo%20/Bar/Baz.txt', exec_lua('return vim.uri.from_fname(filepath)'))
 
-      it('file path including white space', function()
-        exec_lua([[filepath = 'C:\\Foo \\Bar\\Baz.txt']])
+      exec_lua([[filepath = 'C:\\xy\\åäö\\ɧ\\汉语\\↥\\🤦\\🦄\\å\\بِيَّ.txt']])
+      eq(
+        'file:///C:/xy/%c3%a5%c3%a4%c3%b6/%c9%a7/%e6%b1%89%e8%af%ad/%e2%86%a5/%f0%9f%a4%a6/%f0%9f%a6%84/a%cc%8a/%d8%a8%d9%90%d9%8a%d9%8e%d9%91.txt',
+        exec_lua('return vim.uri.from_fname(filepath)')
+      )
+    end)
 
-        eq('file:///C:/Foo%20/Bar/Baz.txt', exec_lua('return vim.uri_from_fname(filepath)'))
-      end)
-
-      it('file path including Unicode characters', function()
-        exec_lua([[filepath = 'C:\\xy\\åäö\\ɧ\\汉语\\↥\\🤦\\🦄\\å\\بِيَّ.txt']])
-
-        eq(
-          'file:///C:/xy/%c3%a5%c3%a4%c3%b6/%c9%a7/%e6%b1%89%e8%af%ad/%e2%86%a5/%f0%9f%a4%a6/%f0%9f%a6%84/a%cc%8a/%d8%a8%d9%90%d9%8a%d9%8e%d9%91.txt',
-          exec_lua('return vim.uri_from_fname(filepath)')
-        )
-      end)
+    it('roundtrip to_fname(from_fname(path))', function()
+      local paths =
+        { '/a/c#/b?c', '/a/%25/%A0.txt', '/a b/#@file@#', 'C:/a b/c#', '//server/share/a b' }
+      eq(
+        paths,
+        exec_lua(function()
+          return vim.tbl_map(function(path)
+            return vim.uri.to_fname(vim.uri.from_fname(path))
+          end, paths)
+        end)
+      )
     end)
   end)
 
-  describe('uri to filepath', function()
-    describe('decode Unix file path', function()
-      it('file path includes only ascii characters', function()
-        exec_lua("uri = 'file:///Foo/Bar/Baz.txt'")
+  describe('to_fname()', function()
+    it('Unix filepath', function()
+      exec_lua("uri = 'file:///Foo/Bar/Baz.txt'")
 
-        eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri_to_fname(uri)'))
-      end)
+      eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri.to_fname(uri)'))
 
-      it('local file path without hostname', function()
-        exec_lua("uri = 'file:/Foo/Bar/Baz.txt'")
+      -- Filepath without hostname:
+      exec_lua("uri = 'file:/Foo/Bar/Baz.txt'")
+      eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri.to_fname(uri)'))
+      eq(
+        { '/Foo/Bar', '/Foo/Bar', '/Foo/Bar', '/', '/Foo' },
+        exec_lua(function()
+          local uris = {
+            'file:Foo/Bar',
+            'file:////Foo/Bar',
+            'file://localhost/Foo/Bar',
+            'file://',
+            'FILE:///Foo',
+          }
+          return vim.tbl_map(vim.uri.to_fname, uris)
+        end)
+      )
 
-        eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri_to_fname(uri)'))
-      end)
+      -- Filepath with whitespace:
+      exec_lua("uri = 'file:///Foo%20/Bar/Baz.txt'")
+      eq('/Foo /Bar/Baz.txt', exec_lua('return vim.uri.to_fname(uri)'))
 
-      it('file path including white space', function()
-        exec_lua("uri = 'file:///Foo%20/Bar/Baz.txt'")
+      local test_case = [[
+      local uri = 'file:///xy/%C3%A5%C3%A4%C3%B6/%C9%A7/%E6%B1%89%E8%AF%AD/%E2%86%A5/%F0%9F%A4%A6/%F0%9F%A6%84/a%CC%8A/%D8%A8%D9%90%D9%8A%D9%8E%D9%91.txt'
+      return vim.uri.to_fname(uri)
+      ]]
+      eq('/xy/åäö/ɧ/汉语/↥/🤦/🦄/å/بِيَّ.txt', exec_lua(test_case))
 
-        eq('/Foo /Bar/Baz.txt', exec_lua('return vim.uri_to_fname(uri)'))
-      end)
-
-      it('file path including Unicode characters', function()
-        local test_case = [[
-        local uri = 'file:///xy/%C3%A5%C3%A4%C3%B6/%C9%A7/%E6%B1%89%E8%AF%AD/%E2%86%A5/%F0%9F%A4%A6/%F0%9F%A6%84/a%CC%8A/%D8%A8%D9%90%D9%8A%D9%8E%D9%91.txt'
-        return vim.uri_to_fname(uri)
-        ]]
-
-        eq('/xy/åäö/ɧ/汉语/↥/🤦/🦄/å/بِيَّ.txt', exec_lua(test_case))
-      end)
-
-      it('file path with uri fragment', function()
-        exec_lua("uri = 'file:///Foo/Bar/Baz.txt#fragment'")
-
-        eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri_to_fname(uri)'))
-      end)
+      -- Filepath with uri query, fragment.
+      exec_lua("uri = 'file:///Foo/Bar/Baz.txt?query#fragment'")
+      eq('/Foo/Bar/Baz.txt', exec_lua('return vim.uri.to_fname(uri)'))
     end)
 
-    describe('decode Windows filepath', function()
-      it('file path includes only ascii characters', function()
+    describe('Windows filepath', function()
+      it('filepath includes only ascii characters', function()
         local test_case = [[
         local uri = 'file:///C:/Foo/Bar/Baz.txt'
-        return vim.uri_to_fname(uri)
+        return vim.uri.to_fname(uri)
         ]]
 
-        eq('C:\\Foo\\Bar\\Baz.txt', exec_lua(test_case))
+        eq('C:/Foo/Bar/Baz.txt', exec_lua(test_case))
       end)
 
-      it('local file path without hostname', function()
+      it('local filepath without hostname', function()
         local test_case = [[
         local uri = 'file:/C:/Foo/Bar/Baz.txt'
-        return vim.uri_to_fname(uri)
+        return vim.uri.to_fname(uri)
         ]]
 
-        eq('C:\\Foo\\Bar\\Baz.txt', exec_lua(test_case))
+        eq('C:/Foo/Bar/Baz.txt', exec_lua(test_case))
+        -- Drive letter, not a host.
+        eq(
+          { 'C:/Foo/Bar/Baz.txt', 'C:\\Foo\\Bar', 'C:\\Foo\\Bar' },
+          exec_lua(function()
+            local uris = { 'file://C:/Foo/Bar/Baz.txt', 'file://C:\\Foo\\Bar', 'C:\\Foo\\Bar' }
+            return vim.tbl_map(vim.uri.to_fname, uris)
+          end)
+        )
       end)
 
-      it('file path includes only ascii characters with encoded colon character', function()
+      it('filepath includes only ascii characters with encoded colon character', function()
         local test_case = [[
         local uri = 'file:///C%3A/Foo/Bar/Baz.txt'
-        return vim.uri_to_fname(uri)
+        return vim.uri.to_fname(uri)
         ]]
 
-        eq('C:\\Foo\\Bar\\Baz.txt', exec_lua(test_case))
+        eq('C:/Foo/Bar/Baz.txt', exec_lua(test_case))
       end)
 
-      it('file path including white space', function()
+      it('filepath including white space', function()
         local test_case = [[
         local uri = 'file:///C:/Foo%20/Bar/Baz.txt'
-        return vim.uri_to_fname(uri)
+        return vim.uri.to_fname(uri)
         ]]
 
-        eq('C:\\Foo \\Bar\\Baz.txt', exec_lua(test_case))
+        eq('C:/Foo /Bar/Baz.txt', exec_lua(test_case))
       end)
 
-      it('file path including Unicode characters', function()
+      it('filepath including Unicode characters', function()
         local test_case = [[
         local uri = 'file:///C:/xy/%C3%A5%C3%A4%C3%B6/%C9%A7/%E6%B1%89%E8%AF%AD/%E2%86%A5/%F0%9F%A4%A6/%F0%9F%A6%84/a%CC%8A/%D8%A8%D9%90%D9%8A%D9%8E%D9%91.txt'
-        return vim.uri_to_fname(uri)
+        return vim.uri.to_fname(uri)
         ]]
 
-        eq('C:\\xy\\åäö\\ɧ\\汉语\\↥\\🤦\\🦄\\å\\بِيَّ.txt', exec_lua(test_case))
+        eq('C:/xy/åäö/ɧ/汉语/↥/🤦/🦄/å/بِيَّ.txt', exec_lua(test_case))
+      end)
+
+      it('filepath with host is a UNC path', function()
+        eq('//server/share/a b', exec_lua([[return vim.uri.to_fname('file://server/share/a%20b')]]))
+        if is_os('win') then
+          eq(
+            'file://server/share/a%20b',
+            exec_lua([[return vim.uri.from_fname('\\\\server\\share\\a b')]])
+          )
+        end
       end)
     end)
 
-    describe('decode non-file URI', function()
-      it('uri_to_fname returns non-file URI unchanged', function()
-        eq(
-          'jdt1.23+x-z://content/%5C/',
-          exec_lua [[
-          return vim.uri_to_fname('jdt1.23+x-z://content/%5C/')
-        ]]
-        )
-      end)
+    it('non-file URI returns unchanged', function()
+      eq(
+        'jdt1.23+x-z://content/%5C/',
+        exec_lua [[
+        return vim.uri.to_fname('jdt1.23+x-z://content/%5C/')
+      ]]
+      )
 
-      it('uri_to_fname returns non-file upper-case scheme URI unchanged', function()
-        eq(
-          'JDT://content/%5C/',
-          exec_lua [[
-          return vim.uri_to_fname('JDT://content/%5C/')
-        ]]
-        )
-      end)
+      -- Upper-case scheme returns unchanged.
+      eq(
+        'JDT://content/%5C/',
+        exec_lua [[
+        return vim.uri.to_fname('JDT://content/%5C/')
+      ]]
+      )
 
-      it('uri_to_fname returns non-file scheme URI without authority unchanged', function()
-        eq(
-          'zipfile:///path/to/archive.zip%3A%3Afilename.txt',
-          exec_lua [[
-          return vim.uri_to_fname('zipfile:///path/to/archive.zip%3A%3Afilename.txt')
-        ]]
-        )
-      end)
+      -- Returns URI without authority unchanged.
+      eq(
+        'zipfile:///path/to/archive.zip%3A%3Afilename.txt',
+        exec_lua [[
+        return vim.uri.to_fname('zipfile:///path/to/archive.zip%3A%3Afilename.txt')
+      ]]
+      )
     end)
 
-    describe('decode URI without scheme', function()
-      it('fails because URI must have a scheme', function()
+    describe('URI without scheme', function()
+      it('fails (scheme is required)', function()
         eq(
           false,
           exec_lua [[
-          return pcall(vim.uri_to_fname, 'not_an_uri.txt')
+          return pcall(vim.uri.to_fname, 'not_an_uri.txt')
         ]]
         )
       end)
 
-      it('uri_to_fname should not treat comma as a scheme character', function()
+      it('does not treat comma as a scheme character', function()
         eq(
           false,
           exec_lua [[
-          return pcall(vim.uri_to_fname, 'foo,://bar')
+          return pcall(vim.uri.to_fname, 'foo,://bar')
         ]]
         )
       end)
 
-      it('uri_to_fname returns non-file schema URI with fragment unchanged', function()
+      it('returns non-file scheme URI with fragment unchanged', function()
         eq(
           'scheme://path#fragment',
           exec_lua [[
-          return vim.uri_to_fname('scheme://path#fragment')
+          return vim.uri.to_fname('scheme://path#fragment')
         ]]
         )
       end)
     end)
   end)
 
-  describe('uri from bufnr', function()
+  describe('from_buf()', function()
     it('Windows paths should not be treated as uris', function()
       skip(not is_os('win'), 'N/A on non-Windows')
 
@@ -214,7 +239,7 @@ describe('URI methods', function()
       local test_case = string.format(
         [[
           local file = '%s'
-          return vim.uri_from_bufnr(vim.fn.bufadd(file))
+          return vim.uri.from_buf(vim.fn.bufadd(file))
         ]],
         file
       )
@@ -224,41 +249,117 @@ describe('URI methods', function()
     end)
   end)
 
-  describe('uri to bufnr', function()
-    it('uri_to_bufnr & uri_from_bufnr returns original uri for non-file uris', function()
+  describe('to_buf()', function()
+    it('to_buf & from_buf returns original uri for non-file uris', function()
       local uri =
         'jdt://contents/java.base/java.util/List.class?=sql/%5C/home%5C/user%5C/.jabba%5C/jdk%5C/openjdk%5C@1.14.0%5C/lib%5C/jrt-fs.jar%60java.base=/javadoc_location=/https:%5C/%5C/docs.oracle.com%5C/en%5C/java%5C/javase%5C/14%5C/docs%5C/api%5C/=/%3Cjava.util(List.class'
       local test_case = string.format(
         [[
         local uri = '%s'
-        return vim.uri_from_bufnr(vim.uri_to_bufnr(uri))
+        return vim.uri.from_buf(vim.uri.to_buf(uri))
       ]],
         uri
       )
       eq(uri, exec_lua(test_case))
     end)
 
-    it(
-      'uri_to_bufnr & uri_from_bufnr returns original uri for non-file uris without authority',
-      function()
-        local uri = 'zipfile:///path/to/archive.zip%3A%3Afilename.txt'
-        local test_case = string.format(
-          [[
+    it('to_buf & from_buf returns original uri for non-file uris without authority', function()
+      local uri = 'zipfile:///path/to/archive.zip%3A%3Afilename.txt'
+      local test_case = string.format(
+        [[
         local uri = '%s'
-        return vim.uri_from_bufnr(vim.uri_to_bufnr(uri))
+        return vim.uri.from_buf(vim.uri.to_buf(uri))
       ]],
-          uri
-        )
-        eq(uri, exec_lua(test_case))
-      end
-    )
+        uri
+      )
+      eq(uri, exec_lua(test_case))
+      -- Deprecated aliases.
+      eq(uri, exec_lua('return vim.uri_from_bufnr(vim.uri_to_bufnr(...))', uri))
+    end)
   end)
 
-  describe('encode to uri', function()
+  describe('encode()', function()
     it('rfc2732 including brackets', function()
       exec_lua("str = '[:]'")
       exec_lua("rfc = 'rfc2732'")
-      eq('[%3a]', exec_lua('return vim.uri_encode(str, rfc)'))
+      eq('[%3a]', exec_lua('return vim.uri.encode(str, rfc)'))
+    end)
+
+    it('encode/decode roundtrip', function()
+      eq(
+        { '/a:b@c$d%23%3f%25%20', '%2fa%3ab%40c%24d' },
+        exec_lua(function()
+          return { vim.uri.encode('/a:b@c$d#?% '), vim.uri.encode('/a:b@c$d', 'rfc2396') }
+        end)
+      )
+      -- Hex case, no double-decoding, malformed escapes.
+      eq(
+        'åå %41 %zz%',
+        exec_lua(function()
+          return vim.uri.decode('%c3%a5%C3%A5%20%2541%20%zz%')
+        end)
+      )
+      -- Roundtrips all bytes.
+      eq(
+        {},
+        exec_lua(function()
+          local bytes = {} ---@type string[]
+          for i = 0, 255 do
+            bytes[#bytes + 1] = string.char(i)
+          end
+          local s = table.concat(bytes)
+          local failed = {} ---@type string[]
+          for _, rfc in ipairs({ 'rfc2396', 'rfc2732', 'rfc3986' }) do
+            if vim.uri.decode(vim.uri.encode(s, rfc)) ~= s then
+              failed[#failed + 1] = rfc
+            end
+          end
+          return failed
+        end)
+      )
     end)
   end)
+
+  it('parse()', function()
+    local uris = {
+      'https://u@example.com:80/a%20b?q=1#f?#',
+      'file:///a',
+      'deno:/https/a',
+      'mailto:a@example.com',
+      'inmemory:',
+      'foo:api/files',
+      'f3ile:#d',
+      'file:////shares/p',
+      'stuff:?',
+      'C:/a',
+      '/a',
+    }
+    local parsed = exec_lua(function()
+      return vim.tbl_map(function(uri)
+        local u = vim.uri.parse(uri)
+        -- Roundtrip: tostring() gives the original URI.
+        assert(not u or tostring(u) == uri, uri)
+        return u or {}
+      end, uris)
+    end)
+    eq({
+      {
+        scheme = 'https',
+        authority = 'u@example.com:80',
+        path = '/a%20b',
+        query = 'q=1',
+        fragment = 'f?#',
+      },
+      { scheme = 'file', authority = '', path = '/a' },
+      { scheme = 'deno', path = '/https/a' },
+      { scheme = 'mailto', path = 'a@example.com' },
+      { scheme = 'inmemory', path = '' },
+      { scheme = 'foo', path = 'api/files' },
+      { scheme = 'f3ile', path = '', fragment = 'd' },
+      { scheme = 'file', authority = '', path = '//shares/p' },
+      { scheme = 'stuff', path = '', query = '' },
+      {},
+      {},
+    }, parsed)
+  end)
 end)
diff --git a/test/functional/plugin/lsp/buf_spec.lua b/test/functional/plugin/lsp/buf_spec.lua
index efd4794046..258c397615 100644
--- a/test/functional/plugin/lsp/buf_spec.lua
+++ b/test/functional/plugin/lsp/buf_spec.lua
@@ -1533,7 +1533,7 @@ describe('vim.lsp.buf', function()
                   start = { line = 0, character = 0 },
                   ['end'] = { line = 0, character = 0 },
                 },
-                uri = vim.uri_from_bufnr(bufnr),
+                uri = vim.uri.from_buf(bufnr),
               }
               callback(nil, location)
             end,
@@ -1590,7 +1590,7 @@ describe('vim.lsp.buf', function()
                     start = { line = 0, character = character },
                     ['end'] = { line = 0, character = character },
                   },
-                  uri = vim.uri_from_bufnr(bufnr),
+                  uri = vim.uri.from_buf(bufnr),
                 }
                 callback(nil, location)
               end,
@@ -1704,7 +1704,7 @@ describe('vim.lsp.buf', function()
     it('favors document diagnostics over workspace diagnostics', function()
       local client_id = setup_server({ make_report('full', 'Workspace error', 1) })
       local diagnostic_bufnr = exec_lua(function()
-        return vim.uri_to_bufnr(fake_uri)
+        return vim.uri.to_buf(fake_uri)
       end)
 
       exec_lua(function()
@@ -1740,7 +1740,7 @@ describe('vim.lsp.buf', function()
       eq(
         'Document error',
         exec_lua(function()
-          return vim.diagnostic.get(vim.uri_to_bufnr(fake_uri))[1].message
+          return vim.diagnostic.get(vim.uri.to_buf(fake_uri))[1].message
         end)
       )
     end)
diff --git a/test/functional/plugin/lsp/diagnostic_spec.lua b/test/functional/plugin/lsp/diagnostic_spec.lua
index df530ed472..3d7eb46cab 100644
--- a/test/functional/plugin/lsp/diagnostic_spec.lua
+++ b/test/functional/plugin/lsp/diagnostic_spec.lua
@@ -96,7 +96,7 @@ describe('vim.lsp.diagnostic', function()
     fake_uri = 'file:///fake/uri'
 
     exec_lua(function()
-      diagnostic_bufnr = vim.uri_to_bufnr(fake_uri)
+      diagnostic_bufnr = vim.uri.to_buf(fake_uri)
       local lines = { '1st line', '2nd line of text', 'wow', 'cool', 'more', 'lines' }
       vim.fn.bufload(diagnostic_bufnr)
       vim.api.nvim_buf_set_lines(diagnostic_bufnr, 0, 1, false, lines)
@@ -169,7 +169,7 @@ describe('vim.lsp.diagnostic', function()
             uri = 'file:///fake/uri2',
             diagnostics = {},
           }, { client_id = client_id })
-          return vim.fn.bufnr(vim.uri_to_fname('file:///fake/uri2'))
+          return vim.fn.bufnr(vim.uri.to_fname('file:///fake/uri2'))
         end)
       )
 
@@ -183,7 +183,7 @@ describe('vim.lsp.diagnostic', function()
               _G.make_error('Diagnostic', 0, 0, 0, 0),
             },
           }, { client_id = client_id })
-          return vim.fn.bufnr(vim.uri_to_fname('file:///fake/uri2'))
+          return vim.fn.bufnr(vim.uri.to_fname('file:///fake/uri2'))
         end)
       )
       eq(
@@ -201,7 +201,7 @@ describe('vim.lsp.diagnostic', function()
             uri = 'file:///fake/uri2',
             diagnostics = {},
           }, { client_id = client_id })
-          return vim.fn.bufnr(vim.uri_to_fname('file:///fake/uri2'))
+          return vim.fn.bufnr(vim.uri.to_fname('file:///fake/uri2'))
         end)
       )
       eq(
@@ -766,7 +766,7 @@ describe('vim.lsp.diagnostic', function()
       local fake_uri_2 = 'file:///fake/uri2'
       ---@type vim.Diagnostic[], vim.Diagnostic[], string?
       local diagnostics, related_diagnostics, relatedPreviousResultId = exec_lua(function()
-        local second_buf = vim.uri_to_bufnr(fake_uri_2)
+        local second_buf = vim.uri.to_buf(fake_uri_2)
         vim.fn.bufload(second_buf)
 
         -- Attach the client to both buffers.
@@ -973,7 +973,7 @@ describe('vim.lsp.diagnostic', function()
             _G.doc_requests,
             vim.diagnostic.get(),
             vim.diagnostic.get(diagnostic_bufnr),
-            vim.diagnostic.get(vim.uri_to_bufnr(fake_uri_3))
+            vim.diagnostic.get(vim.uri.to_buf(fake_uri_3))
         end
       )
       eq(1, workspace_requests)
diff --git a/test/functional/plugin/lsp/util_spec.lua b/test/functional/plugin/lsp/util_spec.lua
index 4904bde9aa..169cfd3e60 100644
--- a/test/functional/plugin/lsp/util_spec.lua
+++ b/test/functional/plugin/lsp/util_spec.lua
@@ -266,7 +266,7 @@ describe('vim.lsp.util', function()
       }
       for _, params in ipairs(test_params) do
         local actual = exec_lua(function(params0)
-          local bufnr = vim.uri_to_bufnr('file:///fake/uri')
+          local bufnr = vim.uri.to_buf('file:///fake/uri')
           local lines = { 'testing', '123' }
           vim.api.nvim_buf_set_lines(bufnr, 0, 1, false, lines)
           return vim.lsp.util.locations_to_items(params0, 'utf-16')
@@ -300,12 +300,12 @@ describe('vim.lsp.util', function()
         },
       }
       local actual = exec_lua(function()
-        local bufnr = vim.uri_to_bufnr('file:///fake/uri')
+        local bufnr = vim.uri.to_buf('file:///fake/uri')
         local lines = { 'testing', '123' }
         vim.api.nvim_buf_set_lines(bufnr, 0, 1, false, lines)
         local locations = {
           {
-            targetUri = vim.uri_from_bufnr(bufnr),
+            targetUri = vim.uri.from_buf(bufnr),
             targetRange = {
               start = { line = 0, character = 2 },
               ['end'] = { line = 0, character = 3 },
@@ -688,14 +688,14 @@ describe('vim.lsp.util', function()
 
     before_each(function()
       target_bufnr = exec_lua(function()
-        local bufnr = vim.uri_to_bufnr('file:///fake/uri')
+        local bufnr = vim.uri.to_buf('file:///fake/uri')
         local lines = { '1st line of text', 'å å ɧ 汉语 ↥ 🤦 🦄' }
         vim.api.nvim_buf_set_lines(bufnr, 0, 1, false, lines)
         return bufnr
       end)
 
       target_bufnr2 = exec_lua(function()
-        local bufnr = vim.uri_to_bufnr('file:///fake/uri2')
+        local bufnr = vim.uri.to_buf('file:///fake/uri2')
         local lines = { '1st line of text', 'å å ɧ 汉语 ↥ 🤦 🦄' }
         vim.api.nvim_buf_set_lines(bufnr, 0, 1, false, lines)
         return bufnr
@@ -1099,7 +1099,7 @@ describe('vim.lsp.util', function()
     describe('stylize_markdown', function()
       local stylize_markdown = function(content, opts)
         return exec_lua(function()
-          local bufnr = vim.uri_to_bufnr('file:///fake/uri')
+          local bufnr = vim.uri.to_buf('file:///fake/uri')
           vim.fn.bufload(bufnr)
           return vim.lsp.util.stylize_markdown(bufnr, content, opts)
         end)
diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 2161199f4c..b921de93f3 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -2615,7 +2615,7 @@ describe('LSP', function()
 
     before_each(function()
       target_bufnr = exec_lua(function()
-        local bufnr = vim.uri_to_bufnr('file:///fake/uri')
+        local bufnr = vim.uri.to_buf('file:///fake/uri')
         local lines = { '1st line of text', '2nd line of 语text' }
         vim.api.nvim_buf_set_lines(bufnr, 0, 1, false, lines)
         return bufnr
@@ -2746,7 +2746,7 @@ describe('LSP', function()
 
     before_each(function()
       exec_lua(function()
-        target_bufnr = vim.uri_to_bufnr('file:///fake/uri')
+        target_bufnr = vim.uri.to_buf('file:///fake/uri')
         local lines = {
           'Original Line #1',
           'Original Line #2',
@@ -2813,7 +2813,7 @@ describe('LSP', function()
 
     it('supports file creation with CreateFile payload', function()
       local tmpfile = tmpname(false)
-      local uri = exec_lua('return vim.uri_from_fname(...)', tmpfile)
+      local uri = exec_lua('return vim.uri.from_fname(...)', tmpfile)
       local edit = {
         documentChanges = {
           {
@@ -2832,7 +2832,7 @@ describe('LSP', function()
       'supports file creation in folder that needs to be created with CreateFile payload',
       function()
         local tmpfile = tmpname(false) .. '/dummy/x/'
-        local uri = exec_lua('return vim.uri_from_fname(...)', tmpfile)
+        local uri = exec_lua('return vim.uri.from_fname(...)', tmpfile)
         local edit = {
           documentChanges = {
             {
@@ -2851,7 +2851,7 @@ describe('LSP', function()
     it('createFile does not touch file if it exists and ignoreIfExists is set', function()
       local tmpfile = tmpname()
       write_file(tmpfile, 'Dummy content')
-      local uri = exec_lua('return vim.uri_from_fname(...)', tmpfile)
+      local uri = exec_lua('return vim.uri.from_fname(...)', tmpfile)
       local edit = {
         documentChanges = {
           {
@@ -2871,7 +2871,7 @@ describe('LSP', function()
     it('createFile overrides file if overwrite is set', function()
       local tmpfile = tmpname()
       write_file(tmpfile, 'Dummy content')
-      local uri = exec_lua('return vim.uri_from_fname(...)', tmpfile)
+      local uri = exec_lua('return vim.uri.from_fname(...)', tmpfile)
       local edit = {
         documentChanges = {
           {
@@ -2895,7 +2895,7 @@ describe('LSP', function()
       local uri = exec_lua(function()
         local bufnr = vim.fn.bufadd(tmpfile)
         vim.fn.bufload(bufnr)
-        return vim.uri_from_fname(tmpfile)
+        return vim.uri.from_fname(tmpfile)
       end)
       local edit = {
         documentChanges = {
@@ -2912,7 +2912,7 @@ describe('LSP', function()
 
     it('DeleteFile fails if file does not exist and ignoreIfNotExists is false', function()
       local tmpfile = tmpname(false)
-      local uri = exec_lua('return vim.uri_from_fname(...)', tmpfile)
+      local uri = exec_lua('return vim.uri.from_fname(...)', tmpfile)
       local edit = {
         documentChanges = {
           {
@@ -4287,7 +4287,7 @@ describe('LSP', function()
                       },
                       {
                         globPattern = {
-                          baseUri = vim.uri_from_fname(root_dir),
+                          baseUri = vim.uri.from_fname(root_dir),
                           pattern = '{foo}',
                         },
                         kind = 7,
@@ -4341,7 +4341,7 @@ describe('LSP', function()
             return { logfile = logfile, messages = server.messages, notifications = notifications }
           end)
 
-          local uri = vim.uri_from_fname(root_dir .. '/watch')
+          local uri = vim.uri.from_fname(root_dir .. '/watch')
           local messages = result.messages
 
           eq(6, #messages)
@@ -4439,7 +4439,7 @@ describe('LSP', function()
           eq({
             method = 'workspace/didChangeWatchedFiles',
             params = {
-              changes = { { uri = vim.uri_from_fname(root_dir .. '/file.py'), type = created } },
+              changes = { { uri = vim.uri.from_fname(root_dir .. '/file.py'), type = created } },
             },
           }, result)
         end
@@ -4508,7 +4508,7 @@ describe('LSP', function()
       end)
 
       local function watched_uri(fname)
-        return vim.uri_from_fname(root_dir .. '/' .. fname)
+        return vim.uri.from_fname(root_dir .. '/' .. fname)
       end
 
       eq(4, #result)
@@ -4548,7 +4548,7 @@ describe('LSP', function()
         for i = 0, max_kind do
           table.insert(watchers, {
             globPattern = {
-              baseUri = vim.uri_from_fname('/dir[1]'),
+              baseUri = vim.uri.from_fname('/dir[1]'),
               pattern = 'watch' .. tostring(i),
             },
             kind = i,
@@ -4580,7 +4580,7 @@ describe('LSP', function()
       end)
 
       local function watched_uri(fname)
-        return vim.uri_from_fname('/dir[1]/' .. fname)
+        return vim.uri.from_fname('/dir[1]/' .. fname)
       end
 
       eq(3, #result)
@@ -4685,15 +4685,15 @@ describe('LSP', function()
         changes = {
           {
             type = created,
-            uri = vim.uri_from_fname('file1'),
+            uri = vim.uri.from_fname('file1'),
           },
           {
             type = changed,
-            uri = vim.uri_from_fname('file1'),
+            uri = vim.uri.from_fname('file1'),
           },
           {
             type = created,
-            uri = vim.uri_from_fname('file2'),
+            uri = vim.uri.from_fname('file2'),
           },
         },
       }, result[3].params)
diff --git a/test/functional/plugin/pack_spec.lua b/test/functional/plugin/pack_spec.lua
index bbe0b2f26a..c294381e66 100644
--- a/test/functional/plugin/pack_spec.lua
+++ b/test/functional/plugin/pack_spec.lua
@@ -1590,10 +1590,10 @@ describe('vim.pack', function()
 
         local fetch_src = repos_src.fetch
         local fetch_path = pack_get_plug_path('fetch')
-        local fetch_path_uri = vim.uri_from_fname(fetch_path)
+        local fetch_path_uri = vim.uri.from_fname(fetch_path)
         local semver_src = repos_src.semver
         local semver_path = pack_get_plug_path('semver')
-        local semver_path_uri = vim.uri_from_fname(semver_path)
+        local semver_path_uri = vim.uri.from_fname(semver_path)
 
         -- With `file://` sources it can only return "Path:" and "Source:" links
         local ref_file_links = {
diff --git a/test/functional/plugin/zip_spec.lua b/test/functional/plugin/zip_spec.lua
index 95b760fb05..219e2c80eb 100644
--- a/test/functional/plugin/zip_spec.lua
+++ b/test/functional/plugin/zip_spec.lua
@@ -248,6 +248,11 @@ describe('nvim.zip', function()
 
       eq({ 'plain text' }, lines())
       eq(false, exec_lua('return vim.b.nvim_dir ~= nil'))
+
+      -- Ignores a URL.
+      n.command('edit deno:/x/a.zip')
+      poke_eventloop()
+      eq({ '', '' }, { vim.trim(n.exec_capture('messages')), n.eval('v:errmsg') })
     end)
 
     it('lists a valid empty archive as empty', function()
diff --git a/test/old/testdir/test_gf.vim b/test/old/testdir/test_gf.vim
index c82dc1705c..17b79080ff 100644
--- a/test/old/testdir/test_gf.vim
+++ b/test/old/testdir/test_gf.vim
@@ -1,7 +1,7 @@
 " Test for the gf and gF (goto file) commands
 
 " This is a test if a URL is recognized by "gf", with the cursor before and
-" after the "://".  Also test ":\\".
+" after the "://".  Nvim: ":\\" is not a URL.
 func Test_gf_url()
   enew!
   call append(0, [
@@ -22,10 +22,11 @@ func Test_gf_url()
   set isf=@,48-57,/,.,-,_,+,,,$,~,\
   call search("^third")
   call search("name")
-  call assert_equal("URL:\\\\machine.name\\vimtest2c", expand("<cfile>"))
+  " Nvim: Backslashes "\" not supported in URLs, thus "URL:" is ignored.
+  call assert_equal("\\\\machine.name\\vimtest2c", expand("<cfile>"))
   call search("^fourth")
   call search("URL")
-  call assert_equal("URL:\\\\machine.name\\tmp\\vimtest2d", expand("<cfile>"))
+  call assert_equal("URL", expand("<cfile>"))
 
   call search("^fifth")
   call search("URL")
diff --git a/test/unit/path_spec.lua b/test/unit/path_spec.lua
index 5d9edc8d9e..eb9d50bc57 100644
--- a/test/unit/path_spec.lua
+++ b/test/unit/path_spec.lua
@@ -744,47 +744,48 @@ describe('path.c', function()
       end
 
       -- Check normal scheme with just alphabetic
-      eq(1, path_with_url([[test://xyz/foo/b0]]))
-      eq(2, path_with_url([[test:\\xyz\foo\b0]]))
+      eq(true, path_with_url([[test://xyz/foo/b0]]))
+      eq(false, path_with_url([[test:\\xyz\foo\b0]]))
 
       -- Check valid scheme with just alphanumeric
-      eq(1, path_with_url([[test123://xyz/foo/b0]]))
-      eq(2, path_with_url([[test123:\\xyz\foo\b0]]))
+      eq(true, path_with_url([[test123://xyz/foo/b0]]))
+      eq(false, path_with_url([[test123:\\xyz\foo\b0]]))
 
       -- Check invalid scheme (contains invalid character)
-      eq(0, path_with_url([[test_abc://xyz/foo/b2]]))
+      eq(false, path_with_url([[test_abc://xyz/foo/b2]]))
 
       -- Check valid scheme containing '+', '-', or '.'
-      eq(1, path_with_url([[test+abc://xyz/foo/b1]]))
-      eq(2, path_with_url([[test+abc:\\xyz\foo\b1]]))
-      eq(1, path_with_url([[test-abc://xyz/foo/b3]]))
-      eq(2, path_with_url([[test-abc:\\xyz\foo\b3]]))
-      eq(1, path_with_url([[test.abc://xyz/foo/b1]]))
-      eq(2, path_with_url([[test.abc:\\xyz\foo\b1]]))
+      eq(true, path_with_url([[test+abc://xyz/foo/b1]]))
+      eq(false, path_with_url([[test+abc:\\xyz\foo\b1]]))
+      eq(true, path_with_url([[test-abc://xyz/foo/b3]]))
+      eq(false, path_with_url([[test-abc:\\xyz\foo\b3]]))
+      eq(true, path_with_url([[test.abc://xyz/foo/b1]]))
+      eq(false, path_with_url([[test.abc:\\xyz\foo\b1]]))
 
       -- Check valid scheme with full suite of allowed characters
-      eq(1, path_with_url([[test+abc-123.ghi://xyz/foo/b1]]))
-      eq(2, path_with_url([[test+abc-123.ghi:\\xyz\foo\b1]]))
+      eq(true, path_with_url([[test+abc-123.ghi://xyz/foo/b1]]))
+      eq(false, path_with_url([[test+abc-123.ghi:\\xyz\foo\b1]]))
 
       -- Check invalid scheme starting or ending with '+', '-', or '.'
-      eq(0, path_with_url([[-test://xyz/foo/b4]]))
-      eq(0, path_with_url([[test-://xyz/foo/b5]]))
-      eq(0, path_with_url([[+test://xyz/foo/b4]]))
-      eq(0, path_with_url([[test+://xyz/foo/b5]]))
-      eq(0, path_with_url([[.test://xyz/foo/b4]]))
-      eq(0, path_with_url([[test.://xyz/foo/b5]]))
+      eq(false, path_with_url([[-test://xyz/foo/b4]]))
+      eq(false, path_with_url([[test-://xyz/foo/b5]]))
+      eq(false, path_with_url([[+test://xyz/foo/b4]]))
+      eq(false, path_with_url([[test+://xyz/foo/b5]]))
+      eq(false, path_with_url([[.test://xyz/foo/b4]]))
+      eq(false, path_with_url([[test.://xyz/foo/b5]]))
 
       -- Check additional valid scheme containing '+', '-', or '.'
-      eq(1, path_with_url([[test-C:/xyz/foo/b5]]))
-      eq(1, path_with_url([[test-custom:/xyz/foo/b5]]))
-      eq(1, path_with_url([[test+C:/xyz/foo/b5]]))
-      eq(1, path_with_url([[test+custom:/xyz/foo/b5]]))
-      eq(1, path_with_url([[test.C:/xyz/foo/b5]]))
-      eq(1, path_with_url([[test.custom:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test-C:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test-custom:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test+C:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test+custom:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test.C:/xyz/foo/b5]]))
+      eq(true, path_with_url([[test.custom:/xyz/foo/b5]]))
 
       -- Check invalid scheme representing drive letter
-      eq(0, path_with_url([[c:/xyz/foo/b5]]))
-      eq(0, path_with_url([[C:/xyz/foo/b5]]))
+      eq(false, path_with_url([[c:/xyz/foo/b5]]))
+      eq(false, path_with_url([[C:/xyz/foo/b5]]))
+      eq(false, path_with_url([[C:\xyz\foo\b5]]))
     end)
   end)
 end)