Performance Testing
Real Core Web Vitals,
not a vanity score.
Paste a URL. We run a full Rocket Vitals scan with real Chromium metrics, then surface the performance findings first.
Free to start. Full site scan in about 90 seconds — performance issues are prioritized in the report.
Ranking factor
Core Web Vitals
Lab + field
Chromium metrics + CrUX INP
Image audit
Format, size & lazy load
Load blockers
Render-blocking JS & CSS
What we check
Lab metrics, field INP, and the resources that slow the page.
We measure what users feel — then list the blockers to fix.
Core Web Vitals (LCP, CLS, INP)
Measures LCP, CLS, and INP. INP uses real CrUX field data where available.
First Contentful Paint
Tracks FCP and flags slow (>3s) and needs-improvement (1.8–3s) results.
Render-blocking resources
Identifies CSS and JavaScript that block rendering and hurt every timing metric.
Image optimization
Flags oversized images, missing lazy-loading, absent srcset, and non-modern formats.
Server response time (TTFB)
Tests Time to First Byte — a slow origin compounds every downstream problem.
Compression & HTTP/2
Detects responses without gzip/Brotli and sites not using HTTP/2 multiplexing.
Font loading
Catches fonts served without font-display — a common, fixable LCP killer.
CDN & caching signals
Checks whether static assets use a CDN and whether the LCP image is preloaded.
Rocket Vitals by Rocket Park
Scan for performance issues.
You get LCP/CLS evidence and the render-blocking resources behind them — not a letter grade.
Scan for performance issues →