> ## Documentation Index
> Fetch the complete documentation index at: https://docs.browspark.krishm.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# devtools_performance

> Performance panel.

Performance panel. start/stop a trace recording (Chrome trace format, opens in DevTools Performance and Perfetto). stop returns a summary: time by category, long tasks with their heaviest children, script time by URL, observed LCP/FCP/CLS, user timings. search finds trace events by name/args. compare diffs two recordings. vitals reads live Web Vitals (LCP, CLS, INP, FID, FCP, TTFB, long tasks) observed in the page since the session started. metrics returns Chrome runtime metrics.

## Parameters

<ParamField body="tabId" type="integer">
  Target tab id from browser\_tabs, which lists tabs across all windows. Defaults to the agent's most recently opened usable tab, or the only usable tab. Otherwise select a listed tabId.
</ParamField>

<ParamField body="action" type="enum" required>
  One of: `start`, `stop`, `search`, `compare`, `vitals`, `metrics`, `list`.
</ParamField>

<ParamField body="categories" type="string[]">
  Trace categories (default: devtools timeline + v8)
</ParamField>

<ParamField body="screenshots" type="boolean">
   
</ParamField>

<ParamField body="reload" type="boolean">
  start: reload the page right after tracing begins (page-load profile)
</ParamField>

<ParamField body="recordingId" type="string">
   
</ParamField>

<ParamField body="other" type="string">
  compare: second recording
</ParamField>

<ParamField body="query" type="string">
   
</ParamField>

<ParamField body="regex" type="boolean">
   
</ParamField>

<ParamField body="minDurationMs" type="number">
   
</ParamField>

<ParamField body="offset" type="integer">
  Pagination offset, default 0 Range: 0 to ….
</ParamField>

<ParamField body="limit" type="integer">
  Page size, default 50 Range: 1 to 500.
</ParamField>

## Example

```json theme={null}
{
  "tabId": 1234,
  "action": "start",
  "reload": true,
  "screenshots": false
}
```

```json theme={null}
{
  "tabId": 1234,
  "action": "stop"
}
```

```json Live Web Vitals theme={null}
{
  "tabId": 1234,
  "action": "vitals"
}
```