Guide
Improving page performance findings
Read Core Web Vitals results, find the biggest opportunities, and know what to fix first.
5 min read
What the performance score measures
The performance score is based on Lighthouse metrics captured in a real headless browser. The main signals are Largest Contentful Paint (LCP), Total Blocking Time (TBT), Cumulative Layout Shift (CLS), First Contentful Paint (FCP), and Speed Index. LCP and TBT have the most weight.
Fix LCP first
LCP measures when the largest image or text block on the page finishes loading. Common causes: an unoptimised hero image, no preload hint for the largest asset, or server response time above 600ms. Compress images to WebP, add a preload link for the hero, and ensure the server responds in under 200ms.
Reduce layout shift
CLS is caused by elements that move after they load: images without width and height attributes, web fonts that swap, or late-injected banners. Reserve space for images, use font-display: optional or swap, and avoid inserting content above existing content after load.
Reduce render-blocking scripts
TBT is driven by JavaScript that blocks the browser's main thread. Audit third-party scripts, defer analytics and tag managers, and split large JavaScript bundles. The resource waterfall in the report shows which scripts delay interactive.