Performance
Performance measures how fast a page loads for real users, based on Google PageSpeed Insights / Lighthouse scores. Weight: 2.5%.
Details
Google PageSpeed Insights
The performance data is sourced from the Google PageSpeed Insights API, which runs Lighthouse against the URL. The API returns a Performance score from 0–100 based on Core Web Vitals and other speed metrics.
Important: Unlike other categories that start at 100 and deduct, the Performance category uses the PageSpeed score as its base. A page scoring 50 on PageSpeed starts at 50, not 100. Additional deductions apply for server response time >3 seconds (−10 pts).
Core Web Vitals (2026)
Google uses three Core Web Vitals as ranking signals:
• LCP (Largest Contentful Paint) — how fast the main content loads. Target: < 2.5s
• CLS (Cumulative Layout Shift) — how much the layout shifts during load. Target: < 0.1
• INP (Interaction to Next Paint) — responsiveness to user input (replaced FID in March 2024). Target: < 200ms
The audit reports FCP (First Contentful Paint), LCP, TBT (Total Blocking Time, a proxy for INP), CLS, Speed Index, and TTI (Time to Interactive).
Opportunities
PageSpeed Insights also returns a list of optimisation opportunities — specific actions like 'Serve images in next-gen formats', 'Eliminate render-blocking resources', or 'Reduce unused JavaScript'. These are reported as-is from the Lighthouse audit and provide actionable guidance for improving load speed.
Why performance weight is low
Performance contributes only 2.5% to the overall audit score. This reflects Google's own guidance: page speed is a ranking factor but it operates as a tiebreaker. Strong content, technical fundamentals, and authority matter more. A fast but empty page will not rank.
Metrics
| Metric | Description |
|---|---|
| PageSpeed score | Lighthouse performance score from Google PageSpeed Insights (0–100). Used as base score for this category. |
| FCP | First Contentful Paint — time until the first text or image appears. |
| LCP | Largest Contentful Paint — time for the main content element to appear. Target: < 2.5s. |
| TBT | Total Blocking Time — total time the main thread is blocked by long tasks. Proxy for INP. |
| CLS | Cumulative Layout Shift — visual stability of the page. Target: < 0.1. |
| Speed Index | How quickly the contents of the page are visually populated. |
| TTI | Time to Interactive — when the page becomes fully interactive. |
| Opportunities | List of specific optimisation suggestions from Lighthouse. |
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