diff --git a/lib/phoenix/socket/transport.ex b/lib/phoenix/socket/transport.ex
index 1514723335..a09c778b89 100644
--- a/lib/phoenix/socket/transport.ex
+++ b/lib/phoenix/socket/transport.ex
@@ -269,7 +269,7 @@ defmodule Phoenix.Socket.Transport do
 
     connect_info =
       Enum.map(connect_info, fn
-        key when key in [:peer_data, :trace_context_headers, :uri, :user_agent, :x_headers, :auth_token] ->
+        key when key in [:peer_data, :trace_context_headers, :uri, :user_agent, :x_headers, :sec_websocket_headers, :auth_token] ->
           key
 
         {:session, session} ->
@@ -280,7 +280,7 @@ defmodule Phoenix.Socket.Transport do
 
         other ->
           raise ArgumentError,
-                ":connect_info keys are expected to be one of :peer_data, :trace_context_headers, :x_headers, :uri, or {:session, config}, " <>
+                ":connect_info keys are expected to be one of :peer_data, :trace_context_headers, :x_headers, :user_agent, :sec_websocket_headers, :uri, or {:session, config}, " <>
                   "optionally followed by custom keyword pairs, got: #{inspect(other)}"
       end)
 
@@ -470,6 +470,8 @@ defmodule Phoenix.Socket.Transport do
 
     * `:user_agent` - the value of the "user-agent" request header
 
+    * `:sec_websocket_headers` - a list of all request headers that have a "sec-websocket-" prefix
+
   The CSRF check can be disabled by setting the `:check_csrf` option to `false`.
   """
   def connect_info(conn, endpoint, keys, opts \\ []) do
@@ -482,7 +484,7 @@ defmodule Phoenix.Socket.Transport do
           {:trace_context_headers, fetch_trace_context_headers(conn)}
 
         :x_headers ->
-          {:x_headers, fetch_x_headers(conn)}
+          {:x_headers, fetch_headers(conn, "x-")}
 
         :uri ->
           {:uri, fetch_uri(conn)}
@@ -490,6 +492,9 @@ defmodule Phoenix.Socket.Transport do
         :user_agent ->
           {:user_agent, fetch_user_agent(conn)}
 
+        :sec_websocket_headers ->
+          {:sec_websocket_headers, fetch_headers(conn, "sec-websocket-")}
+
         {:session, session} ->
           {:session, connect_session(conn, endpoint, session, opts)}
 
@@ -527,9 +532,9 @@ defmodule Phoenix.Socket.Transport do
     end
   end
 
-  defp fetch_x_headers(conn) do
+  defp fetch_headers(conn, prefix) do
     for {header, _} = pair <- conn.req_headers,
-        String.starts_with?(header, "x-"),
+        String.starts_with?(header, prefix),
         do: pair
   end
 
diff --git a/test/phoenix/integration/websocket_channels_test.exs b/test/phoenix/integration/websocket_channels_test.exs
index 2bd0a49c9a..7f3125252f 100644
--- a/test/phoenix/integration/websocket_channels_test.exs
+++ b/test/phoenix/integration/websocket_channels_test.exs
@@ -121,6 +121,7 @@ defmodule Phoenix.Integration.WebSocketChannelsTest do
         |> Map.update!(:trace_context_headers, &Map.new/1)
         |> Map.update!(:uri, &Map.from_struct/1)
         |> Map.update!(:x_headers, &Map.new/1)
+        |> Map.update!(:sec_websocket_headers, &Map.new/1)
 
       socket =
         socket
@@ -191,8 +192,9 @@ defmodule Phoenix.Integration.WebSocketChannelsTest do
           :peer_data,
           :uri,
           :user_agent,
+          :sec_websocket_headers,
           session: @session_config,
-          signing_salt: "salt"
+          signing_salt: "salt",
         ]
       ]
 
@@ -328,6 +330,35 @@ defmodule Phoenix.Integration.WebSocketChannelsTest do
           }
         end
 
+        test "transport sec-websocket-* headers are extracted to the socket connect_info" do
+          extra_headers = [
+            {"sec-websocket-protocol", "phoenix, 123"},
+            {"sec-websocket-extensions", "permessage-deflate; client_max_window_bits=15"}
+          ]
+
+          {:ok, sock} =
+            WebsocketClient.connect(
+              self(),
+              "ws://127.0.0.1:#{@port}/ws/connect_info/websocket?vsn=#{@vsn}",
+              @serializer,
+              extra_headers
+            )
+
+          WebsocketClient.join(sock, lobby(), %{})
+
+          assert_receive %Message{
+            event: "joined",
+            payload: %{
+              "connect_info" => %{
+                "sec_websocket_headers" => %{
+                  "sec-websocket-protocol" => "phoenix, 123",
+                  "sec-websocket-extensions" => "permessage-deflate; client_max_window_bits=15"
+                }
+              }
+            }
+          }
+        end
+
         test "transport trace_context_headers are extracted to the socket connect_info" do
           extra_headers = [
             {"traceparent", "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01"},