Core Web Vitals Checker

The Core Web Vitals Checker is a free online tool that check and understand your core web vitals (lcp, inp, cls, fcp, ttfb, tbt) with educational guidance and optimization tips.. It runs entirely in your browser with no installation or sign-up needed.

No. Enter values from PageSpeed Insights, Lighthouse, or CrUX. The tool evaluates them against Google thresholds with color-coded results and optimization tips.

LCP (loading), INP (interactivity, replaced FID in March 2024), and CLS (visual stability). All three must be "Good" to pass Google CWV assessment.

LCP: <2.5s good, >4s poor. INP: <200ms good, >500ms poor. CLS: <0.1 good, >0.25 poor. FCP: <1.8s good, >3s poor. TTFB: <800ms good, >1800ms poor. TBT: <200ms good, >600ms poor.

Yes, the Core Web Vitals Checker is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Core Web Vitals Checker processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Core Web Vitals Checker is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Core Web Vitals Checker in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Yes, the Core Web Vitals Checker is built following current Google Search guidelines and best practices. We regularly update the tool to reflect changes in search engine requirements.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

Lab data comes from a single test in a controlled environment, like Lighthouse in Chrome DevTools or the Lighthouse section of PageSpeed Insights. It is repeatable and great for debugging, but it reflects one simulated device and network rather than your real visitors. Field data comes from the Chrome User Experience Report (CrUX), which collects anonymized measurements from actual Chrome users on your live page. Google uses field data, not lab data, to assess Core Web Vitals for ranking, evaluating performance at the 75th percentile of real visits. That is why a page can score well in Lighthouse yet still fail in Search Console. Note that INP and TTFB are field metrics, while TBT is lab-only. Paste whichever numbers you have into this checker to see exactly where each metric falls against Google's thresholds.

First Input Delay (FID) only measured the delay before the browser began processing your very first interaction on a page. It ignored everything that happened after the click started and every interaction that followed, so a page could score a perfect FID while still feeling sluggish whenever you typed or tapped a menu. Interaction to Next Paint (INP) fixes this by observing the latency of all clicks, taps, and key presses across the entire visit and reporting a value near the worst case. It captures how responsive the page feels throughout the session, not just at the start. Google made INP an official Core Web Vital in March 2024, retiring FID. The Good threshold is 200ms or less and Poor is over 500ms. Enter your INP value above to grade it and see targeted tips for breaking up long main-thread tasks.

Google applies the same thresholds to both desktop and mobile, but it scores them with separate field data, and mobile is usually harder to pass. Phones have slower CPUs, less memory, and higher network latency, which inflates loading and responsiveness metrics like LCP, INP, and TBT. The same JavaScript that runs instantly on a laptop can block a mid-range phone's main thread for far longer. Because Google primarily uses mobile CrUX data to rank pages in mobile search, a desktop pass does not guarantee a mobile pass. PageSpeed Insights reports mobile and desktop separately for exactly this reason, so always check both. Enter your mobile numbers in this checker first, since that is the form factor most likely to hurt your rankings, then compare against your desktop results to see which metrics need work.

When Google assesses your Core Web Vitals from field data, it does not use your average load time or your best load. It looks at the 75th percentile of real visits over a rolling 28-day window, meaning a metric must hit the Good threshold for at least 75 percent of page loads to pass. Put simply, three out of every four visits need to be Good. Using the 75th percentile instead of the average prevents a handful of very fast loads from masking a slow experience for many users, while still ignoring the slowest outliers caused by rare conditions. This is why optimizing only your test machine is not enough; you have to improve the experience for the bulk of real visitors. Enter the 75th-percentile values from PageSpeed Insights or CrUX into this checker to see whether each metric clears the bar.

No. Only three metrics are official Core Web Vitals: LCP for loading, INP for interactivity, and CLS for visual stability. Your overall pass-or-fail verdict depends solely on those three, and all three must land in the Good range to pass. FCP, TTFB, and TBT are diagnostic metrics that do not directly factor into the assessment but explain why a core vital is struggling. A slow TTFB delays every later metric because nothing renders until the first byte arrives, FCP shows how quickly the first content paints, and TBT acts as a lab proxy for INP by exposing heavy JavaScript during load. Fixing them often improves the core vitals as a side effect. This checker grades all six, drives the overall verdict only from the three core vitals, and surfaces fixes for each so you can trace a poor score back to its root cause.