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SSE & EventSource Debugger

Connect to SSE streams, log event frames with inter-chunk latency, and pretty-print JSON payloads.

Network & APIs
Privacy: 100% Client-Side. Your data never leaves this browser tab. Processing uses Web APIs and client-side libraries only.

Connect to any Server-Sent Events URL with the browser EventSource API. Logs chunk latency and pretty-prints JSON event payloads — useful for LLM streaming and backend push debugging. Subject to CORS.

Status: closed · 0 events
TimeΔ msTypeData
No events yet — connect to a stream.

Why inspect SSE streams?

Server-Sent Events deliver a unidirectional text/event-stream over HTTP. LLM APIs and notification backends often stream token deltas this way. Debugging requires watching event types, payloads, and timing between chunks.

stbox opens a browser EventSource against your URL (CORS permitting), logs each frame, formats JSON data, and shows delta milliseconds between events.

How to use this tool

  1. Paste an SSE URL (or pick a preset) and click Connect.
  2. Watch the live table for type, data, timestamp, and Δ ms.
  3. Disconnect or clear when finished. Cross-origin streams need Access-Control-Allow-Origin.

Frequently asked questions

Why did my stream fail immediately?

Most production SSE endpoints block browsers via CORS. Use a same-origin proxy, a CORS-enabled demo URL, or a local server that allows your origin.