Pico API › SSE Tester
Test server-sent events right in your browser. Connect to a real SSE endpoint and watch events arrive live — or run a simulation to see how streaming responses render. Everything runs client-side; nothing is uploaded anywhere.
A simulated token-by-token stream — the same chunk-by-chunk rendering Pico API shows for real responses.
Leave the URL empty and press Connect for a built-in demo stream — generated locally by a service worker, works offline. Or paste an SSE endpoint you're developing against; it must allow cross-origin requests (CORS) and use https:// (http://localhost is fine).
Each token or event appears the moment it arrives — nothing waits for the response to finish. A status dot shows the connection state, a counter tracks elapsed time and chunk count, and a Stop button aborts mid-stream. This mirrors how Pico API's response panel renders streaming bodies: chunk-by-chunk accumulation, per-chunk timing, auto-scroll, and abort while streaming.
text/event-stream) without writing a scratch scriptThis page is limited by the browser's EventSource API — it cannot send Authorization headers, and it only reaches endpoints that send permissive CORS headers. The Pico API extension isn't bound by these limits:
text/event-stream — NDJSON, LLM completions, plain chunked HTMLEventSource cannot send Authorization headers and requires the endpoint to allow cross-origin requests. Most real APIs fail one of these checks — that's exactly what the Pico API extension works around via its service worker.
Usually not from this page: those endpoints require an auth header, which EventSource can't send. Pico API sends them like any other request and renders the token stream live.
No. This page is plain static HTML; the connection is made by your browser directly to the endpoint you paste. There are no analytics and no backend.