This Core Web Vitals checker runs Google PageSpeed Insights for any URL and shows the three metrics that make up Core Web Vitals, judged against the thresholds Google publishes. A page passes when all three are in the good range at the 75th percentile of real visits:
| Metric | What it measures | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP | When the main content has loaded | ≤ 2.5 s | 2.5–4 s | > 4 s |
| INP | How quickly the page responds to taps, clicks and keys | ≤ 200 ms | 200–500 ms | > 500 ms |
| CLS | How much the layout jumps while loading | ≤ 0.1 | 0.1–0.25 | > 0.25 |
The results also include First Contentful Paint and Time to First Byte from the same field data, Lighthouse lab metrics, the four Lighthouse category scores and the opportunities with the largest estimated savings.
Field data or lab data: which one counts for SEO?
Field data. It comes from the Chrome UX Report: the 75th percentile of real Chrome visits over the previous 28 days. Google says this is the data behind the Core Web Vitals report in Search Console, and that Core Web Vitals are used by its ranking systems as part of page experience. Lab data is a single simulated load, ideal for finding causes and checking a fix before real users see it.
Keep the weight in proportion. The same Google documentation says relevance comes first and that good page experience does not guarantee a top ranking. Our view: fix vitals that are poor, because they cost you visitors regardless of rankings, then move on to content and crawlability.
How to read the results
- Assessment. Passed means LCP, INP and CLS are all good at the 75th percentile. If INP has no data, the verdict uses LCP and CLS.
- Metric cards. Green, amber and red follow the thresholds above. The marker on each bar shows where your value falls.
- Origin data. When a URL lacks traffic, the numbers cover the whole site, which can hide a slow template.
- Lab metrics. Total Blocking Time stands in for INP, since a lab test makes no real interactions. A high TBT usually means heavy JavaScript.
- Opportunities. Estimated savings from Lighthouse. Start with the largest, and re-test after each change.
What usually fixes each metric
- Slow LCP: a slow server response, a large hero image, or render-blocking CSS and fonts. Serve the main image at the right size, do not lazy-load it, and preload it if it is discovered late.
- Slow INP: long JavaScript tasks on the main thread. Split them up, ship less script, and load third-party tags after the page is interactive.
- High CLS: images, embeds and ads without reserved space, banners injected above content, and late-loading web fonts. Set width and height attributes and reserve slots before content arrives.
Why does my page have no field data?
The Chrome UX Report only publishes data for pages and origins with enough eligible visits from Chrome users who share usage statistics (CrUX documentation). New, low-traffic or private pages often have none. That is normal and does not count against you; use the lab results and check again once traffic builds.
Methodology and limits
We call the PageSpeed Insights API with the strategy you choose. Mobile tests emulate a mid-range phone on a throttled connection; desktop tests use a faster profile. Lab scores move a few points between runs, so compare trends rather than single numbers. Identical requests within ten minutes return the cached result, and each visitor can run a limited number of tests per hour because the API has a daily quota. When the quota is used up, the checker says so and links to Google's own PageSpeed Insights page.
Speed is one part of a technical review. The technical SEO checklist covers the rest, and the meta tag checker handles the tags that shape how the page appears in results.
Frequently asked questions
- Are Core Web Vitals a ranking factor?
- Google says Core Web Vitals are used by its ranking systems as part of page experience, but relevance and content quality come first. Treat good vitals as a baseline for users rather than a lever for big ranking gains.
- Why are my lab and field results so different?
- Lab data is one load on an emulated device and network. Field data is the 75th percentile of many real visits on real phones and connections, including cached and repeat views, and it covers interactions that a lab test never makes.
- What does it mean when the results show origin data?
- The Chrome UX Report did not have enough visits to this exact URL, so PageSpeed Insights fell back to the aggregate for the whole origin. It is still real-user data, just not specific to this page.
- How long until my fixes show up?
- Lab results change as soon as you deploy. Field data is a rolling 28-day window, so improvements appear gradually and are fully reflected about four weeks after the fix.
- What happened to First Input Delay?
- Interaction to Next Paint replaced First Input Delay as the responsiveness metric in March 2024. INP looks at the latency of interactions throughout the visit, not only the first one.