Core Web Vitals Checker

Enter your site's measured metrics from Chrome DevTools, PageSpeed Insights, or CrUX data. Get an instant pass/fail assessment against Google's thresholds and specific fix recommendations.

Core Web Vitals

LCP(Largest Contentful Paint)

Good: ≤2500ms · Needs work: ≤4000ms · Poor: >4000ms

INP(Interaction to Next Paint)

Good: ≤200ms · Needs work: ≤500ms · Poor: >500ms

CLS(Cumulative Layout Shift)

Good: ≤0.1 · Needs work: ≤0.25 · Poor: >0.25

FCP(First Contentful Paint)

Good: ≤1800ms · Needs work: ≤3000ms · Poor: >3000ms

TTFB(Time to First Byte)

Good: ≤800ms · Needs work: ≤1800ms · Poor: >1800ms

JavaScript Budget

Total JS (parsed + executed)

Budget: ≤100KB excellent · ≤200KB good · ≤350KB borderline · >350KB over budget

Fix Recommendations

LCP

Preload your largest image with <link rel="preload">. Use a CDN. Consider SSR or SSG to eliminate server latency.

INP

Break up long tasks with scheduler.yield() or setTimeout(0). Avoid heavy event handlers — debounce input and defer non-critical updates.

CLS

Always set explicit width/height on images and embeds. Reserve space for ads and dynamically injected content using aspect-ratio CSS.

FCP

Inline your critical CSS. Remove render-blocking scripts. Ensure TTFB is fast — FCP can never beat TTFB.

TTFB

Enable HTTP/2 or HTTP/3. Add edge caching (Vercel Edge, Cloudflare). Reduce server processing time — check database query times.

Enter your metrics from PageSpeed Insights or Chrome DevTools → Lighthouse to see your score and recommendations.

Thresholds sourced from web.dev/vitals. JS budget based on Alex Russell's 2023 mobile-first guidance.