API Request Tester
Web & network Network on demand
WebSocket & SSE Tester
User-triggered connectionOpen real realtime connections, inspect traffic, measure sessions, reconnect, and export evidence.
Idle
Browser WebSocket cannot set arbitrary handshake headers or expose Ping/Pong frames; mixed-content rules apply.
Connect to capture protocol events.
How to use it
- 01
Configure a connection
Choose WebSocket or SSE, enter the endpoint, and set subprotocols or Fetch Stream headers within browser limits.
- 02
Inspect live traffic
Connect explicitly, send WebSocket payloads, filter timestamped events, and inspect text, JSON, binary, IDs, and sizes.
- 03
Diagnose and export
Review reconnect activity, traffic rates and byte totals, pause rendering under load, and export a bounded JSONL session.
Frequently asked questions
Can I set WebSocket handshake headers?
No. The browser WebSocket API accepts a URL and subprotocols but does not expose arbitrary handshake headers or Ping/Pong control frames.
What is the difference between the SSE modes?
Native EventSource provides browser-managed reconnect but no custom headers. Fetch Stream can send allowed headers and exposes every parsed event field, subject to CORS.
Why was my insecure connection blocked?
A secure HTTPS page cannot freely open insecure ws:// or http:// mixed content. Use TLS-enabled wss:// or HTTPS endpoints.
Are captured messages saved?
No. Endpoints, headers, and traffic stay in memory unless you explicitly download the current bounded session as JSONL.
Related tools
Keep working with other focused browser utilities.