Why did that call fire?
Each call is tied to the click or form submit that caused it, and Details shows "Called from": the page functions that made it, with the timing split (DNS, connect, TLS, waiting, download).
Find wasted calls
- RAPID 140ms the same request twice in a moment, often an effect that runs twice.
- N+1 one call per item in a list, where one batched call would do.
- Performance lists the heaviest endpoints; the Timeline shows what waited on what.
See every UI state without touching the backend
Mock an empty list, an error, a slow answer or a dropped connection, and check your loading, empty and error screens. Pause a call with a breakpoint to edit it on the way. How to mock an API response.
GraphQL, streams and sockets
GraphQL calls are told apart by operation and errors inside a 200 OK are flagged; load the schema and captured calls are checked against it. Server-sent events and token streams (read with fetch, XMLHttpRequest or EventSource) show their events live, with error events, a missing end marker and long pauses flagged, and WebSocket frames are listed with the calls. To see how a page copes, rewrite a reply with a script or slow the whole tab down (both Chrome), or make an endpoint fail with a mock set that stays on.