SSE inspector

Trace captures Server-Sent Events (SSE) streams and records each event as it arrives, so you can inspect real-time push data without a desktop tool.

How SSE capture works

When Trace sees a response with Content-Type: text/event-stream, it treats the connection as an SSE stream and begins parsing events incrementally according to the WHATWG SSE specification. Events are stored as they arrive, so you see a growing timeline even while the connection is still open.

SSE capture works in all three capture modes. HTTPS connections require the root CA to be trusted.

Navigate to SSE connections

SSE streams appear in the Network tab. Use the type filter bar to select SSE and focus the list on streaming traffic only.

Each row in the list shows:

• Protocol badge (SSE)
• Connection status (connecting, streaming, closed, failed)
• Total event count
• Duration of the stream
• Endpoint URL
• Total bytes transferred
• Truncated badge if the stream exceeded the configured body storage limit

Tap a row to open the stream detail view.

Inspect a stream

Stream overview

• URL – the SSE endpoint
• Status – lifecycle state of the connection
• Start / end time and total duration
• Request headers – sent with the initial GET (including Accept: text/event-stream and Last-Event-ID if reconnecting)
• Response headers – including Cache-Control, Connection, and any CORS headers

Event list

Each captured SSE event contains:

| Field | Description | |---|---| | Event ID (id:) | Optional identifier set by the server for reconnect support | | Event type (event:) | Named event type, defaults to message if omitted | | Data (data:) | One or more data lines joined as the payload | | Retry (retry:) | Reconnection interval in milliseconds, if the server sent one | | Timestamp | When Trace received and parsed the event |

Tap an event to view its full data payload. JSON payloads render with syntax highlighting.

Filter events within a stream

Use the filter bar inside a stream detail view to narrow events by:

• Event type – show only message, update, error, or any custom type
• Event ID – search for a specific ID value
• Data content – search within event payloads

Export

SSE sessions are exported as part of a HAR export. To capture a long-running SSE stream before clearing capture data, save the session first:

1. End or pause the capture session.
2. Open Export → HAR or use the share action from the session.

Modifying SSE events

You can intercept and modify SSE event payloads using Custom scripts with a Stream script type. The stream object in JavaScript exposes the event payload so you can rewrite or drop individual events before they reach the client.

Breakpoints also support stream events — set a breakpoint that matches the SSE endpoint to pause and edit individual events in the inspector before they are forwarded.

Troubleshooting

• No SSE entries: verify the target endpoint returns Content-Type: text/event-stream. Trace detects SSE by content type. Also confirm capture is active.
• Stream shows as truncated: increase the Body Storage inline threshold in Advanced Settings, or export the session before it truncates.
• Events missing: some clients reconnect after a timeout using Last-Event-ID. Trace records each reconnection as a continuation of the same stream when the ID field is present.