Is the WebSocket proxied through a server?

No. Your browser opens the connection directly to the target. trydevtools is not in the data path.

Why does wss:// fail when ws:// works?

wss:// requires a valid TLS certificate. Self-signed certs will be rejected unless you add an exception in your browser. ws:// is also blocked from HTTPS pages (mixed content).

Can I send authentication headers?

Browsers don't allow arbitrary headers on the WebSocket handshake. Common workarounds: pass a token in the URL query string, or in a subprotocol via the Sec-WebSocket-Protocol header.

Can I send binary frames?

Yes. The tester accepts hex or base64 input for binary payloads, and incoming binary frames are shown in hex with a copy-as-base64 option.

websocket · ws · wss · live · local

Test WebSocket endpoints

Connect to any ws:// or wss:// URL, send messages, watch the wire log. Subprotocols supported. Runs entirely in your browser.

WebSocket Tester

URL

wss://echo.websocket.o…

tls

State

closed

Sent

frames

Received

frames

input · send frame

output · message log

No messages yet — click Connect to start.

Quick Start

How to test a WebSocket

Drop in a ws:// or wss:// URL, click Connect, and exchange frames. Useful for debugging server behavior before writing client code.

01
Type the URL
wss:// for TLS, ws:// for plain (browsers block ws:// on https pages).
Lookups reference the IANA registries (MIME, HTTP status, TLDs) bundled at build time — no live network calls, no rate limits, no leaked queries.
urlIANAregistryofflinelive
url · querywss · IANA
```
wss://...
```
loaded · IANA bundlespec · ready
02
Optional subprotocols
Comma-separated. The server picks one or rejects the handshake.
Builders emit canonical syntax per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs) so the output passes spec-compliant parsers.
subprotRFC 9110canonicalspec-compliantlive
proto · optionslist · live
```
json, msgpack
```
options applied · livecanonical
03
Connect
The wire log shows the handshake status, close code, and any errors.
Validation flags common pitfalls — uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8 — before they bite production.
connectvalidationlintpitfallslive
state · looked upopen · ready
```
Connected
```
result · livevalidated
04
Send + observe
Send any string; the server's response appears in the log.
Copy writes the snippet directly into your clipboard; downloads emit the right extension and MIME so curl/httpie pick them up correctly.
sendclipboardMIME-correctblobcurl-ready
ok · copiedecho · done
```
↑ hello · ↓ hello
```
shipped · ready to shipsuccess

Pro tips

Web-spec details that bite later

Idempotency saves retries

POST/PUT/DELETE should be safely retried. Use idempotency keys and return the same response on duplicate requests.

Match RFC 9110 status codes

Don’t invent codes. 422 for validation errors, 409 for conflicts, 429 for rate limits. Standard codes work with off-the-shelf clients.

Set <code>Cache-Control</code> deliberately

Default browser caching is conservative. Use max-age + stale-while-revalidate for hot endpoints.

Validate Open Graph in dev

OG tags break silently. Use a previewer like OG Generator + Facebook’s debugger before launch.

CORS is a server concern

The browser sends the preflight; the server decides. Wildcard origins disable credentials — be explicit.

MIME drives behaviour

Servers must send the right Content-Type. Browsers sniff but the spec says they shouldn’t — be explicit to avoid surprises.

Use Cases

When to test WebSockets

Realtime backend QA, protocol design, chat / game / IoT.

Backend smoke test

Quick check that your endpoint accepts handshakes. Bundled from IANA registries at build time — no live network call, no rate limit, no leaked queries. The MIME, TLD, and status-code tables are baked in so the tool works offline once loaded.

spec-compliant

Protocol replay

Replay messages without writing a client. Output is canonical per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs), so spec-compliant parsers accept it as-is. Cross-browser and cross-library behaviour stays consistent.

offline

Echo + ping checks

Verify heartbeat/keepalive logic. Pairs with the curl-to-fetch converter for end-to-end test stubs — copy the curl from DevTools, paste, get an idiomatic fetch() body. Drop into Playwright/Vitest fixtures without manual translation.

IANA-backed

Mock server checks

Hand-debug a development WS server. Catches common pitfalls (uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8) before they bite production. Validation flags rather than auto-corrects so you stay in control.

RFC-aligned

Connection lifecycle

Inspect close codes when the server drops you. Validation runs as you type — copy only when the output is shaped correctly. The output drops directly into nginx, Apache, or CDN configs without re-formatting or re-quoting.

production-grade

Third-party feeds

Tap into public WS feeds (markets, sports, etc). Same input plus same options always produces identical canonical output, so the tool is safe to embed in CI scripts that diff against expected configs.

curl-ready

FAQ

Frequently asked questions

Can I send binary?

This tester sends UTF-8 strings. For binary frames you'd need a custom client — the log displays binary message sizes.

Why does ws:// fail?

Browsers block insecure WS from HTTPS pages. Use wss:// or test from http://localhost.

What does close code 1006 mean?

Abnormal closure — usually a network drop, TLS error, or the server killed the connection.

Is anything logged?

No. Connection lifecycle and messages stay in your browser; we don't proxy or log traffic.

Does it run locally?

Yes — the connection is direct from your browser to the WebSocket endpoint.

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Something missing?

Tell us what you need. We ship the top requests every two weeks.

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