WebSocket
Connect, send, and receive WebSocket messages with Testnizer's full-featured WS editor.
Testnizer’s WebSocket editor keeps a persistent connection alive for as long as you need it. Messages flow in both directions in a single timeline, and the connection survives tab switches.
Opening a WebSocket tab
Click + New → WebSocket (or pick WebSocket from the project sidebar).
You can also import an existing ws:// or wss:// request from Postman or
Insomnia collections.
Connect panel
URL
ws:// and wss:// are both supported. Variables resolve in real time:
wss://{{wsHost}}/chat?room={{roomId}}Headers
Add custom headers to the HTTP upgrade request. Common use cases:
Authorization: Bearer {{token}}Sec-WebSocket-Protocol: graphql-ws(for GraphQL subscriptions that need it)- Custom cookies (set the
Cookieheader directly)
Some WebSocket servers reject unknown headers during the upgrade. Testnizer sends exactly the headers you define, nothing more.
Connect / Disconnect
Hit Connect to perform the upgrade. The status indicator turns green and shows the connection state (Connecting → Open → Closed). Hit Disconnect to send a clean close frame.
If the server rejects the upgrade (non-101 HTTP response) the error message and HTTP response headers are shown in the timeline so you can diagnose auth failures or protocol mismatches.
Sending messages
Message composer
The composer at the bottom of the editor lets you type or paste a message before sending. Choose the format:
- Text — sent as a UTF-8 text frame
- JSON — same as text, but Testnizer validates JSON syntax and auto-formats the composer area
- Binary — paste hex (
0xDEADBEEF) or Base64 (data:) and Testnizer converts to binary frame
Hit Send or press Ctrl+Enter / Cmd+Enter.
Saved messages
Frequently-used messages (ping frames, subscription payloads) can be saved in the Saved messages panel on the right. Click a saved message to pre-fill the composer, then tweak and send.
Message timeline
Every sent and received message appears in the central timeline in chronological order:
- Blue bubble, → arrow — message you sent
- Green bubble, ← arrow — message from server
- Grey line — connect / disconnect / error events
Click any timeline entry to see the full payload in the detail panel. Large payloads are truncated in the timeline (first 256 bytes) but shown in full in the detail view.
Timeline controls
| Control | Action |
|---|---|
| Clear | Removes all timeline entries (does not disconnect) |
| Pause | Stops new entries from scrolling in while you inspect an existing one |
| Filter | Text search across all payloads |
| Show sent / received | Toggle visibility of each direction |
Ping / Pong
Testnizer responds automatically to server ping frames with a pong frame. You can also send a manual ping from the message composer (Type → Ping).
Reconnect
If the connection drops, Testnizer shows a Reconnect button in the timeline. The composer and saved messages are preserved so you can resume without re-entering payloads.
Auto-reconnect with back-off is on the roadmap for v1.1.
Variables in messages
{{variable}} substitution works in the message composer at send time. The
variable is resolved from the active environment (and project variables) each
time you press Send, so you can change an environment value between sends
without editing the message itself.
Connection lifetime
WebSocket connections are tied to the Testnizer tab, not the Electron window. Switching to another tab does not disconnect. Closing the tab sends a clean close frame.