Core Web Vitals checker

What the checker does

You enter your LCP, INP and CLS values and choose mobile or desktop. The checker compares each value with Google's published thresholds and returns one of three grades per metric: good, needs improvement or poor. It then gives an overall result for the page.

It does not crawl your site. It reads numbers you already have and explains them in plain language.

The inputs

Use the field data from real visitors over the previous 28 days, not the lab score. Google uses field data for its assessment. With too little traffic, lab numbers are a rough guide only.

The thresholds it applies

Each value is judged at the 75th percentile. That means three out of four visits must meet the threshold, so a few fast sessions on a good connection do not rescue a slow page.

How to read the result

Work from the weakest metric. The overall result is only as good as your worst grade, so one poor score fails the page even if the other two are good.

Worked example. A product page returns LCP 3.1 s, INP 240 ms and CLS 0.04. LCP and INP both fall in needs improvement. CLS is good. The page does not pass. The checker lists LCP first, because the hero image is the most common cause of a slow LCP and is usually the quickest fix.

• LCP is high: look at the largest image or heading block, its file size, server response time and whether it loads late.
• INP is high: look at heavy JavaScript, third-party scripts and long tasks that block taps and clicks.
• CLS is high: look at images without set dimensions, late-loading banners, ads and web fonts that swap in.

What the result cannot tell you

• It cannot find the cause. A grade says how bad a page is, not why. That needs a trace in browser developer tools.
• It grades one page. Your home page can pass while a template used by thousands of product pages fails.
• It does not predict rankings. Core Web Vitals are one ranking signal among many, and relevance of content still counts for more.

A page that fails is not an emergency. Fix the template behind it first, then re-test once the field data refreshes, which takes about four weeks.

What to do after you get the grade

If everything is good, set a monthly reminder to re-check after releases and plugin updates. Speed usually slips because of a new script, not because of a big redesign. Our website maintenance service covers that routine.

If something fails, work through the Core Web Vitals checklist or read how to improve Core Web Vitals. If you would rather have someone trace the cause across your templates, that is part of technical SEO. You get a fixed quote after a short call: contact us.