Core Web Vitals / PageSpeed Checker

Shows real performance score, LCP, CLS, TBT and FCP metrics via the Google PageSpeed Insights API.

When should you use this?

Use this to measure a page's Core Web Vitals performance (LCP, CLS, INP) after launch or after making a change.

When shouldn't you use this?

A single measurement isn't definitive; network conditions and device performance affect the test result, confirming over time with real user data is more reliable.

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Step-by-step

Type the full address of the page into the Site URL field, including https://. Your busiest product or article page is often more useful to test than the homepage.
Pick mobile or desktop from the Device list. Google mainly looks at the mobile version for ranking, so start with mobile.
Click Run and wait for the PageSpeed Insights response. It can take a little longer than a few seconds.
Check the overall performance score, then LCP, CLS, TBT and FCP one by one. Run the same page again with the other device option.

Example

Say you just added a large hero image to a blog post. A mobile test afterwards may show a higher LCP, which usually means the largest visible element, that hero image, is loading late. Compress it or convert it to a lighter format like WebP, then test again to see the difference. If CLS is high, something is probably pushing content down while the page loads, such as an ad slot or an image without set dimensions.

What are Core Web Vitals?

Core Web Vitals are the three main metrics Google uses to measure page experience: LCP (loading time of the largest content), INP (responsiveness to interaction) and CLS (layout shift). The usual targets are LCP of 2.5 seconds or less, INP of 200 milliseconds or less and CLS of 0.1 or less. These values can be measured with real user data and lab tests.

When improving the metrics

For LCP, compress large images, serve them at the right size and prioritise their loading.
For INP, reduce heavy JavaScript and split long tasks.
For CLS, define sizes up front for images and ad slots.
Lab and real-user data can differ; look at both.

Things to keep in mind

Google's general thresholds: an LCP of 2.5 seconds or less and a CLS of 0.1 or less count as good. These metrics tell you more than the headline score.
TBT is a lab measurement and doesn't replace INP, which measures real user interaction. A high TBT is a good hint to look at heavy JavaScript.
Password-protected pages, pages only reachable on a local network and localhost addresses can't be tested. The page has to be publicly available.
Testing the same page a few minutes apart can move the score by a few points. Look at several runs before deciding anything.

Frequently asked questions

Does this tool directly affect my Google ranking?

No, these are analysis/generation aids; actual ranking depends on many factors. But correct metadata and structured data helps search engines understand your page better.

How should I use the results?

You can paste the generated code/text directly into your site's relevant HTML section (e.g. <head>) or your CMS's SEO settings.

Do you store my data?

No, the URL/text you enter isn't stored anywhere, it's only processed in your browser.