Test a WebSocket from your browser: connect to ws:// or wss://, send text, JSON or real binary frames from HEX/Base64, read binary messages as HEX, and see close codes with reasons. Messages go straight to your server, not ours.
Messages appear here. No WebSocket connection is opened until you press Connect.
This sends an ordinary text message on a timer. It is not a protocol-level ping frame — web pages cannot send or see ping/pong frames. Off by default, because a server that does not expect it may close the connection.
Built and verified by the Go Tools engineering team.
Yes in Chrome after you allow local network access It depends on the browser (as of October 2026). Chrome 147 and later first asks whether the page may access devices on your local network; after you choose Allow, ws://localhost and ws:// to a LAN IP address connect. Firefox connects to localhost directly but blocks LAN addresses. Safari blocks ws:// from HTTPS pages.
The browser hides the reason When the handshake fails, browsers are required to give the page only error and close code 1006 — never the HTTP status or reason. Press F12: the Chrome and Edge console shows the status code the server returned.
Browsers cannot set headers No. The browser WebSocket API has no way to set request headers. Put the token in a URL parameter, a subprotocol or a cookie — whichever your server accepts.
It is an ordinary message No. Web pages cannot send or see protocol-level ping/pong frames; the browser answers server pings by itself. Timed send here is an ordinary text message on an interval, and it is off by default.
Use the Socket.IO preset Socket.IO is not plain WebSocket. Choose the Socket.IO preset: it connects to /socket.io/?EIO=4&transport=websocket, replies 40 to the open packet and answers each ping 2 with pong 3 (Socket.IO v3/v4).
A WebSocket tester is a client you point at a WebSocket server to see whether it accepts a connection and what it sends back. You enter a ws:// or wss:// address, connect, send text or binary messages and read the replies — the quickest way to check a backend endpoint, a reverse proxy or a device that speaks WebSocket without writing client code.
This tester runs in your browser: the connection goes straight from your browser to the server you enter, and messages do not pass through go-tools servers. That also means it has the browser's limits. It cannot add custom request headers, it cannot send protocol-level ping frames, and when a handshake fails the browser tells the page only close code 1006, not why.
What it adds over a bare browser console: binary messages shown as HEX (or Base64) and sent from HEX or Base64 as real binary frames, JSON formatted automatically, close codes explained, a checklist when a connection fails, a warning before connecting when the browser is likely to block the address, and a log that stays responsive at about 2,000 messages per second (measured).
09:30:01.204 · Connecting to ws://localhost:8080/ws
09:30:01.219 · Connected · subprotocol: chat
09:30:02.517 → TXT 17 B {"type":"hello"}
09:30:02.531 ← TXT 25 B {"type":"hello","ok":true}
09:30:03.002 → BIN 4 B 48 69 00 FF
09:30:03.010 ← BIN 4 B 48 69 00 FF
09:30:09.880 · Closed · code 4001: application-defined code Before you connect, the tool checks the address: a plain ws:// to a domain name from this HTTPS page will be blocked, so it says so and suggests wss://. For localhost and LAN IP addresses it tells you Chrome will ask for local network access, and how Firefox and Safari differ (as of October 2026).
Received binary messages are shown as HEX, 16 bytes per line, or as Base64. Type bytes as 48 69 00 FF, 0x48,0x69 or Base64 and they go out as a binary message; invalid characters and odd digit counts are reported with their position, and the byte preview shows exactly what will be sent.
Every close shows the code, the reason text and whether the closing handshake completed, with the meaning of standard codes 1000–1015 and a note for 4000–4999 application codes. A failure before the connection opens produces a checklist instead of a guess.
Messages are drawn once per frame, so the page stays responsive at about 2,000 messages per second in our tests. Each entry has direction, millisecond timestamp, type and byte size. Filter by direction, search, pause the view, keep the last N entries, copy or export as text.
Request one or more subprotocols (comma-separated) and see whether the server confirmed one. A connection timeout ends handshakes the server never answers. The Socket.IO preset completes the Engine.IO v4 handshake and answers pings for you.
Timed send repeats a message of your choice at an interval, and auto-reconnect retries with exponential backoff after an unexpected drop. Both are off by default, and the tool never sends anything you did not ask for.
ws://localhost:8080/ws
Connected
→ TXT 17 B {"type":"hello"}
← TXT 25 B {"type":"hello","ok":true} In Chrome 147 and later the browser first asks whether to allow access to your local network; choose Allow. Firefox connects to localhost directly; Safari blocks ws:// from this HTTPS page (as of October 2026).
48 69 00 FF
→ BIN 4 B 48 69 00 FF
In HEX mode the tool sends a binary message with these four bytes, not the text 48 69 00 FF. Base64 SGkA/w== sends the same four bytes.
Server closes with code 4001, reason "token expired"
Closed · code 4001: application-defined code · clean close Reason: token expired
Codes 4000–4999 are defined by the application, so look up 4001 in the server's documentation. Codes 1000–1015 are standard and are explained in the log.
Protocol: Socket.IO v3/v4, address ws://localhost:3000
Connecting to ws://localhost:3000/socket.io/?EIO=4&transport=websocket
← 0{"sid":"…","pingInterval":25000,…}
→ 40
← 40{"sid":"…"} The preset fills in the Socket.IO path and query, replies 40 to join the default namespace and answers each ping 2 with 3. Send events as 42["event","data"].
Type or paste a ws:// or wss:// address; http:// and https:// are treated as ws:// and wss://. Check the note under the address: it warns when the browser is likely to block it.
Some servers require a subprotocol, for example mqtt. Enter one or more, comma-separated. After connecting, the log shows which one the server confirmed.
Press Connect. For localhost or a LAN address in Chrome, choose Allow when asked about local network access. If the connection fails, follow the checklist that appears.
Choose Text, HEX or Base64, check the preview and press Ctrl+Enter. Received JSON is formatted and binary is shown as HEX; switch binary to Base64 in the log toolbar.
Filter by direction or search the log, pause the view during a flood, then copy or export the log as text with timestamps, direction and byte sizes.
Browsers block unencrypted ws:// to a domain name from a page loaded over HTTPS (mixed content). Chrome and Firefox refuse at once with a SecurityError. Use wss://; for a LAN server in Chrome, write its IP address (local network access must be allowed).
ws://api.example.com/ws
wss://api.example.com/ws
In text mode 48 69 is sent as the text characters 4, 8, space, 6, 9. Switch to HEX to send the bytes 0x48 0x69 as a binary message.
Text mode: 48 69 → TXT 5 B
HEX mode: 48 69 → BIN 2 B
A Socket.IO server rejects a plain WebSocket at its root path, and without replies to its handshake and pings it closes the connection. Use the Socket.IO preset.
ws://localhost:3000
ws://localhost:3000/socket.io/?EIO=4&transport=websocket
Browsers cannot send an Authorization header with a WebSocket handshake. If your server allows it, pass the token as a URL parameter or a subprotocol instead.
Authorization: Bearer eyJ…
wss://api.example.com/ws?token=eyJ…
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