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Use the Web Vitals API to understand frontend performance by environment, URL, page segment, geography, browser, device, campaign, user, trace, and metric.

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Operations

Common filters include environment, metric, period, url, rating, limit, timeline granularity of 1h, 6h, or 1d, and percentile values p50, p75, p90, p95, or p99. Supported Web Vitals filter fields are page_path, query_string, referrer, country, region, city, timezone, language, device_type, browser, os, utm_source, utm_medium, utm_campaign, provider, model, call_type, finish_reason, error_name, http_status, user_id, trace_id, route, and connection. Breakdown rows include the selected dimension value and may include a country code when segmenting by region or city, so clients can label geographic rows without a second lookup.

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CLI and MCP

Use squasher vitals list, squasher vitals summary, squasher vitals detail, or squasher vitals breakdown --project <project_id> --metric LCP --dimension page_path --percentile p75 --period 24h for terminal workflows. Add repeatable filters with --filter field=value, for example --filter page_path=/pricing --filter country=US. In MCP Code Mode, call search("vitals") before executing. Prefer vitals.summary for a fast project overview, then vitals.breakdown when an agent needs to compare pages, countries, regions, cities, browsers, device types, campaigns, users, or traces.

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Agent handoff

Related: Browser SDK, Next.js SDK.