PageSpeed Insights

What PageSpeed Insights shows

• Performance Score — overall score from 0 to 100
• Core Web Vitals — LCP, INP, CLS (based on field data)
• Lab Data — Lighthouse simulation
• Opportunities — actionable speed improvements
• Diagnostics — detailed technical analysis

Field Data vs Lab Data

• Field Data — real visitor data from Chrome UX Report (28‑day average). The most reliable source.
• Lab Data — one‑time test in a simulated environment (Lighthouse). Useful for debugging, but may differ from real experience.

Score interpretation

• 90–100 — good: maintain current performance.
• 50–89 — needs improvement: optimise.
• 0–49 — poor: urgent fixes required.

Key recommendations

• Eliminate render‑blocking resources — inline critical CSS, use defer/async for JavaScript.
• Properly size images — use srcset and responsive images.
• Serve images in next‑gen formats — WebP, AVIF.
• Reduce unused JavaScript — code splitting, tree shaking.
• Minimise main‑thread work — optimise heavy JS tasks.

API automation

// PageSpeed Insights API call example
const url = 'https://www.googleapis.com/pagespeedonline/v5/runPagespeed';
const response = await fetch(`${url}?url=https://example.com&key=YOUR_API_KEY`);
const data = await response.json();
console.log(data.lighthouseResult.categories.performance.score);