Performance Testing
Real Core Web Vitals,
across all your pages.
Rocket Vitals measures LCP, CLS, and INP on every crawled page — plus render-blocking resources, image weight, server response time, and more.
Google ranking factor
Core Web Vitals
Mobile tested
Separate mobile scores
Image audit
Format, size & lazy load
Load blockers
Render-blocking JS & CSS
What we measure
Every performance signal that affects rankings and users.
Core Web Vitals (LCP, CLS, INP)
Measures Largest Contentful Paint, Cumulative Layout Shift, and Interaction to Next Paint on both desktop and mobile viewports.
First Contentful Paint
Tracks FCP — how quickly the first meaningful content appears — and flags both slow (>3s) and needs-improvement (1.8–3s) results.
Render-blocking resources
Identifies CSS and JavaScript that block the main thread during page load, delaying rendering and hurting every timing metric.
Image optimisation
Flags oversized images, missing lazy-loading on below-fold images, absent srcset attributes, and images not using WebP or AVIF.
Server response time (TTFB)
Tests Time to First Byte — a slow server response compounds every downstream performance problem.
Compression & HTTP/2
Detects responses served without gzip or Brotli compression, and sites not using HTTP/2 for multiplexed delivery.
Font loading
Catches fonts served without font-display, causing invisible text during load — a common and fixable LCP killer.
CDN & caching signals
Checks whether static assets are served from a CDN and whether the LCP candidate image is preloaded.
Rocket Vitals by Rocket Park
See which pages are hurting your Core Web Vitals score.
Enter any URL to get a full site performance audit — page-by-page results with severity ratings and fix priorities your team can act on immediately.
Run a performance test →