Free Core Web Vitals Test
Instantly measure your Core Web Vitals against Google's official thresholds.
What the test measures
Largest Contentful Paint (LCP)
How fast your main content appears. Good: under 2.5s.
Cumulative Layout Shift (CLS)
How much the layout jumps while loading. Good: under 0.1.
Total Blocking Time (TBT)
How long the page stays frozen. Good: under 200 ms.
What you get back
- Real-world LCP, CLS, and TBT metrics
- Simulated visual load timeline
- Clear pass/fail grading against Google's official thresholds
What are Core Web Vitals?
Core Web Vitals are the metrics Google uses to measure real-world page experience: how fast the main content loads, how stable the layout is, and how quickly the page responds. They are part of Google's ranking signals, so slow or jumpy pages can lose visibility in search results.
This free Core Web Vitals test loads your page in a real browser through Google PageSpeed Insights and Lighthouse. It measures Largest Contentful Paint, Cumulative Layout Shift and Total Blocking Time, then grades each one against Google's official good, needs-improvement and poor thresholds.
Every metric comes with plain-English advice on what usually causes the problem and how to fix it, such as compressing hero images, reserving space for ads and embeds, or splitting large JavaScript bundles. No account is needed and results arrive in seconds.
Core Web Vitals Guide: Measure, Understand and Fix
What this Core Web Vitals test does
The test calls the Google PageSpeed Insights API, which runs Lighthouse in a real Chromium browser for both the mobile and desktop strategies at the same time. It reports Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), Total Blocking Time (TBT), First Contentful Paint (FCP) and Speed Index, plus field Interaction to Next Paint (INP) when Chrome UX Report data exists for the URL.
Why Core Web Vitals matter for SEO
Core Web Vitals are part of Google's page experience signals. Slow LCP and unstable layouts increase bounce rate, lower conversions and can cost you positions when competing pages offer similar content.
How to fix a slow Largest Contentful Paint
Compress and resize the hero image, serve it as WebP or AVIF, add fetchpriority="high" to the LCP image and never lazy-load it. Remove render-blocking CSS and JavaScript from the head, use a CDN and reduce server response time (TTFB).
How to fix Cumulative Layout Shift
Always set width and height (or aspect-ratio) on images, videos and iframes. Reserve space for ads and embeds, load web fonts with font-display: swap and avoid inserting banners above existing content after load.
How to reduce Total Blocking Time
Split large JavaScript bundles, defer non-critical scripts, remove unused JavaScript and move heavy third-party tags (chat widgets, trackers) after user interaction.