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.
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.