PageSpeed Insights
Always-on with no setup: performance score, lab metrics, real-user field data and opportunities.
What it is#
PageSpeed Insights is part of the metricsKit base package: **always on — no authorization, no API key**. The service runs performance checks for your site on a schedule and the results land in the performance reports.
- Performance score (0-100, mobile / desktop)
- Lab metrics: LCP, CLS, TBT, FCP, speed index, TTI, server response time
- Real-user field data (CrUX): P75 for LCP / INP / CLS / FCP / TTFB with fast/average/slow distribution
- Opportunities: estimated savings, ranked by impact
What you need to do#
- Nothing: data refreshes automatically roughly every 6 hours.
- Keep the site publicly reachable (PSI crawls with a mobile user agent like a real visitor).
- Occasional missing scores are usually upstream quota or timeouts — the next refresh fills them in.
Note: PSI uses the public API with metricsKit's own server quota; your site needs no credentials and none of your Google quota is consumed.
Reading the score#
| Band | Meaning | Action |
|---|---|---|
| 90-100 (green) | Good | Maintain; watch field data |
| 50-89 (amber) | Needs improvement | Work through the Opportunities list |
| 0-49 (red) | Poor | Prioritise LCP / TBT / CLS |
Tip: The lab score reflects one controlled run; field data (real visitors) is what search engines use for ranking signals. Read both together.
Troubleshooting#
- Empty field data: traffic is not yet enough to enter the public CrUX dataset — only lab data is available.
- Occasional null scores: upstream quota or timeout; the next refresh restores them.
- CLS shown as an integer: CrUX reports CLS ×100; the report divides it back for display.
Related docs#
- AdSense — experience affects RPM (/docs/adsense)
- GSC — search performance (/docs/gsc)