diff --git a/Doc/library/http.server.rst b/Doc/library/http.server.rst
index ae75e6dc5fdcf3..b45ee7e0d997de 100644
--- a/Doc/library/http.server.rst
+++ b/Doc/library/http.server.rst
@@ -376,13 +376,16 @@ provides three different variants:
       :func:`os.listdir` to scan the directory, and returns a ``404`` error
       response if the :func:`~os.listdir` fails.
 
-      If the request was mapped to a file, it is opened. Any :exc:`OSError`
-      exception in opening the requested file is mapped to a ``404``,
-      ``'File not found'`` error. If there was a ``'If-Modified-Since'``
-      header in the request, and the file was not modified after this time,
-      a ``304``, ``'Not Modified'`` response is sent. Otherwise, the content
-      type is guessed by calling the :meth:`guess_type` method, which in turn
-      uses the *extensions_map* variable, and the file contents are returned.
+      If the request did not map to a directory, a file is assumed.  If the
+      file does not exist, and the file name has no extension, then default
+      extensions, if any, are tried.  After an appropriate file name is
+      selected, it is opened. Any :exc:`OSError` exception in opening the
+      requested file is mapped to a ``404``, ``'File not found'`` error. If
+      there was a ``'If-Modified-Since'`` header in the request, and the file
+      was not modified after this time, a ``304``, ``'Not Modified'`` response
+      is sent. Otherwise, the content type is guessed by calling the
+      :meth:`guess_type` method, which in turn uses the *extensions_map*
+      variable, and the file contents are returned.
 
       A ``'Content-type:'`` header with the guessed content type is output,
       followed by a ``'Content-Length:'`` header with the file's size and a
@@ -398,6 +401,9 @@ provides three different variants:
       .. versionchanged:: 3.7
          Support of the ``'If-Modified-Since'`` header.
 
+      .. versionchanged:: 3.12
+         Support for default extensions added.
+
 The :class:`SimpleHTTPRequestHandler` class can be used in the following
 manner in order to create a very basic webserver serving files relative to
 the current directory::
@@ -416,7 +422,8 @@ the current directory::
 
 :class:`SimpleHTTPRequestHandler` can also be subclassed to enhance behavior,
 such as using different index file names by overriding the class attribute
-:attr:`index_pages`.
+:attr:`index_pages`, or locating files with default extensions by overriding
+the class attribute :attr:`default_extensions`.
 
 .. _http-server-cli:
 
@@ -462,6 +469,17 @@ following command runs an HTTP/1.1 conformant server::
 .. versionadded:: 3.11
     ``--protocol`` argument was introduced.
 
+By default, the server uses the exact url to locate file names.  The option
+``-e/--extension`` enables searching for ``.html``/``.htm`` files, or allows
+specifying other extensions::
+
+        python -m http.server --extension             # enables .html/.htm
+        pithon -m http.server --extension .pl .asp    # enables .pl/.asp
+
+.. versionadded:: 3.12
+    ``--ext`` argument was introduced.
+
+
 .. class:: CGIHTTPRequestHandler(request, client_address, server)
 
    This class is used to serve either files or output of CGI scripts from the
diff --git a/Lib/http/server.py b/Lib/http/server.py
index 971f08046d50b5..a67f5511bfe614 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -654,6 +654,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
 
     server_version = "SimpleHTTP/" + __version__
     index_pages = ("index.html", "index.htm")
+    default_extensions = ()
     extensions_map = _encodings_map_default = {
         '.gz': 'application/gzip',
         '.Z': 'application/octet-stream',
@@ -723,6 +724,12 @@ def send_head(self):
         if path.endswith("/"):
             self.send_error(HTTPStatus.NOT_FOUND, "File not found")
             return None
+        # Special case for URLs with no extension.
+        if os.path.splitext(path)[1] == "" and not os.path.exists(path):
+            for extension in self.default_extensions:
+                if os.path.exists(path + extension):
+                    path += extension
+                    break
         try:
             f = open(path, 'rb')
         except OSError:
@@ -1246,7 +1253,7 @@ def _get_best_family(*address):
 
 def test(HandlerClass=BaseHTTPRequestHandler,
          ServerClass=ThreadingHTTPServer,
-         protocol="HTTP/1.0", port=8000, bind=None):
+         protocol="HTTP/1.0", port=8000, bind=None, extensions=None):
     """Test the HTTP request handler class.
 
     This runs an HTTP server on port 8000 (or the port argument).
@@ -1254,6 +1261,7 @@ def test(HandlerClass=BaseHTTPRequestHandler,
     """
     ServerClass.address_family, addr = _get_best_family(bind, port)
     HandlerClass.protocol_version = protocol
+    HandlerClass.default_extensions = extensions
     with ServerClass(addr, HandlerClass) as httpd:
         host, port = httpd.socket.getsockname()[:2]
         url_host = f'[{host}]' if ':' in host else host
@@ -1284,10 +1292,19 @@ def test(HandlerClass=BaseHTTPRequestHandler,
                         default='HTTP/1.0',
                         help='conform to this HTTP version '
                              '(default: %(default)s)')
+    parser.add_argument('-e', '--extension', default=None, nargs='*',
+                        help='extensions to try if none specified in url '
+                             '(default: none; default with -e alone: .html .htm)')
     parser.add_argument('port', default=8000, type=int, nargs='?',
                         help='bind to this port '
                              '(default: %(default)s)')
     args = parser.parse_args()
+    if args.extension is None:
+        ext = ()
+    elif args.extension == []:
+        ext = ('.html', '.htm')
+    else:
+        ext = tuple(args.extension)
     if args.cgi:
         handler_class = CGIHTTPRequestHandler
     else:
@@ -1313,4 +1330,5 @@ def finish_request(self, request, client_address):
         port=args.port,
         bind=args.bind,
         protocol=args.protocol,
+        extensions=ext,
     )
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index cbcf94136ac4eb..d5a3a4e02a113a 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -590,6 +590,21 @@ def test_path_without_leading_slash(self):
         self.assertEqual(response.getheader("Location"),
                          self.tempdir_name + "/?hi=1")
 
+    def test_default_extension(self):
+        # Checks an extensionless path finds a HMTL file, and finds an
+        # extensionless file with priority.
+        self.thread.request_handler.default_extensions = ('.html', )
+        data1 = b"SPAM SPAM SPAM!\r\n"
+        with open(os.path.join(self.tempdir, 'spam.html'), 'wb') as f:
+            f.write(data1)
+        response = self.request(self.base_url + '/spam')
+        self.check_status_and_reason(response, HTTPStatus.OK, data1)
+        data2 = b"The one true spam.\r\n"
+        with open(os.path.join(self.tempdir, 'spam'), 'wb') as f:
+            f.write(data2)
+        response = self.request(self.base_url + '/spam')
+        self.check_status_and_reason(response, HTTPStatus.OK, data2)
+
     def test_html_escape_filename(self):
         filename = '<test&>.txt'
         fullpath = os.path.join(self.tempdir, filename)
diff --git a/Misc/NEWS.d/next/Library/2023-01-04-20-33-14.gh-issue-100463.ofnOye.rst b/Misc/NEWS.d/next/Library/2023-01-04-20-33-14.gh-issue-100463.ofnOye.rst
new file mode 100644
index 00000000000000..219f4f34730423
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-01-04-20-33-14.gh-issue-100463.ofnOye.rst
@@ -0,0 +1,2 @@
+Add support for default extensions in
+``http.server.SimpleHTTPRequestHandler``.