LangStop

WebSocket Client — Test WebSocket APIs Online

WebSocket Client — Test WebSocket Servers in Your Browser

Enter a ws:// or wss:// URL, click Connect, and send messages to a WebSocket server while every frame you send and receive appears in a timestamped log. The connection goes straight from your browser to the server — there is no LangStop relay in between, and nothing is recorded.

How to use it

  1. Pick an endpoint. Type a URL or choose a preset: wss://echo.websocket.org and wss://echo.websocket.events echo back whatever you send, and ws://localhost:8080 is there for a server you are running locally.
  2. Connect. The status indicator turns green when the handshake succeeds; the log records the connection.
  3. Send messages. Type in the box and press Enter to send (Shift+Enter adds a new line). Messages that parse as JSON are marked as JSON in the log.
  4. Read the log. Sent and received messages are listed in order with their time. Turn auto-scroll off to read older messages while new ones keep arriving, and clear the log at any time.
  5. Disconnect. The log shows the close code and reason — 1000 is a normal close; 1006 means the connection dropped without a close frame.

What you can test

  • A new WebSocket endpoint — does the handshake succeed, and does the server answer the first message the way you expect?
  • Message formats — paste a JSON payload and check the server's response before writing client code.
  • A local development server — connect to ws://localhost while you build it.
  • Echo behaviour and latency — use an echo server to confirm your network and proxy allow WebSocket traffic.

Limits of a browser WebSocket client

These come from the browser's WebSocket API, not from this tool:

  • No custom headers. Browsers do not let a page set headers such as Authorization on a WebSocket handshake. Servers that need a token usually accept it as a query parameter (wss://api.example.com/ws?token=…) or as the first message after connecting.
  • Cookies are the browser's. Only cookies the browser already holds for that domain are sent.
  • Mixed content. A page served over HTTPS can only open wss:// connections, except to localhost.
  • Text messages. The client sends text frames; binary frames are not decoded for display.
  • Origin checks. Servers that restrict the Origin header may refuse connections from a page on langstop.com.

Sharing a setup

The share button copies a link that restores the URL, the preset and the message you were composing. It never connects automatically — whoever opens the link presses Connect themselves.