Core Web Vitals Checker
Paste a URL and get the real-user Core Web Vitals Google uses (LCP, INP, CLS), a lab test with a performance score, and the biggest opportunities to fix, for mobile or desktop.
Three metrics decide whether a page passes.
Google evaluates Core Web Vitals on real Chrome visits (the 75th percentile over 28 days). Lab tests help you diagnose, but the field data is what counts for rankings.
How long it takes for the largest visible element (usually a hero image or heading) to render. It is the loading metric visitors feel most.
Good: 2.5 s or lessHow quickly the page responds to taps and clicks across the whole visit. Replaced First Input Delay in 2024. The lab test approximates it with Total Blocking Time.
Good: 200 ms or lessHow much the layout jumps while loading, for example when an image or ad pops in and pushes text down. Measures visual stability.
Good: 0.1 or lessThe fixes that move the needle most often.
The LCP element is almost always an image or a font-dependent heading.
- Serve the hero image in WebP or AVIF, sized for the viewport, with fetchpriority=”high” and never lazy-loaded.
- Cut server response time: page caching, a CDN and a decent host. TTFB above 800 ms drags everything.
- Remove render-blocking CSS and JavaScript from the head; inline the critical CSS.
Slow interactions come from too much JavaScript on the main thread.
- Defer or remove third-party scripts (chat widgets, trackers, A/B tools) that are not needed on first load.
- Break up long tasks and avoid heavy work inside click handlers.
- Check the tag manager: a bloated container is a common INP culprit on WordPress and Shopify sites.
Layout shift is a reservation problem: the browser did not know how much space something needed.
- Set width and height attributes on every image and video.
- Reserve space for ads, embeds and cookie banners.
- Use font-display: swap with size-adjusted fallbacks, or preload the main web font.
A Lighthouse score of 100 is not the goal. Passing all three field metrics on mobile is. Fix the poor metric first, re-measure after 28 days of real traffic, then move on.
- Test the templates that get traffic: home, category, product and article.
- Compare mobile and desktop; mobile is usually the problem.
- Use Search Console’s Core Web Vitals report to see which URL groups fail.
Failing Core Web Vitals on more than one template?
A one-page test tells you where it hurts. A Core Web Vitals audit tells you why, across every template, with the exact fixes your developer needs.
Prioritised, developer-ready findings.
One consultant, start to finish.