Free Core Web Vitals Test

If you last brushed up on Core Web Vitals a couple of years ago, one of the three metrics you memorised no longer exists. In March 2024, Google retired First Input Delay (FID) and replaced it with Interaction to Next Paint (INP). If you've searched "core web vitals INP replaces FID" and come away more confused than before, here's the plain version.

FID only ever measured the delay before the browser started responding to your very first tap or click. It was a low bar, and nearly every site cleared it — which made it close to useless. INP is stricter and a lot fairer: it looks at how responsive interactions are across the whole visit, not just the first one, and reports something near the worst lag a real user hit. A page can no longer coast on a good first impression.

The number to remember is the INP threshold: an INP of 200ms (200 milliseconds) or less is "good," up to 500ms is "needs improvement," and anything slower is poor. If your site felt fine under FID but suddenly looks worse in reports, this switch is almost always why — nothing broke, the ruler just got more honest.

Run this tool, then open the same page's report in Google Search Console, and you might see two different stories. That's not a bug — the two are measuring in completely different ways, and knowing which is which saves a lot of head-scratching.

The test above is lab data: one controlled measurement, from one location, on a simulated device, right now. It's ideal for debugging because it's instant and repeatable. Search Console shows field data — real Core Web Vitals collected from actual Chrome users over the trailing 28 days. That second set is the data Google actually ranks on.

The practical upshot: use a lab test like this one to find and fix problems fast, because you get an answer in seconds instead of waiting weeks for the field data to update. Just remember INP can't truly be measured in a lab — it needs a real person clicking things — so lab tools report Total Blocking Time as its stand-in. Bring TBT down and your real-world INP almost always follows. And if you've ever wondered whether Google PageSpeed is accurate, this is the answer: it is — a lab score just measures something different from the field data Google ranks on.

So does Core Web Vitals affect SEO? The honest answer is yes — but they're a tiebreaker, not a magic wand. They're a confirmed Google ranking signal, which means page speed is a ranking factor, part of the page-experience assessment. Relevance and content quality still do the heavy lifting, though: a blazing-fast page about the wrong thing won't outrank a slower page that genuinely answers the query.

Where speed decides the race is between pages that are otherwise close. When two results are similarly relevant, the faster, more stable one gets the edge — and on mobile, where connections are flaky and patience is thin, that edge is bigger. There's also a knock-on effect people forget: fast pages keep visitors from bouncing straight back to the search results, and they convert better once they land. So even if you set rankings aside entirely, the vitals still pay for themselves.

"Passing" has a precise meaning, and it trips people up. All three core metrics — LCP, INP, and CLS — have to sit in the "good" band for the 75th percentile of your real visitors over 28 days. Not your best visitors, not your fastest test run: three out of every four real page loads have to be good. That bottom quarter — slower phones, worse connections — is usually where a failing assessment is hiding.

If the test above came back with a metric in the red, here's a Core Web Vitals strategy that actually holds up rather than a list of everything you could theoretically do:

The tool at the top of this page is built for the first job: paste a URL, get your LCP, CLS, TBT and the rest in seconds, and know exactly which metric to fix. The numbers match what Google's PageSpeed Insights would give you, because it's the same engine underneath — no sign-up, test as many pages as you like.

But a single score is a photo, and Core Web Vitals are a movie. They drift every time you deploy — a heavier image here, a new third-party script there — and the page that passed last month can slip without anyone noticing until rankings dip. That's the gap Uptura fills: it runs this same test on a schedule, charts every metric over time, and alerts you the moment one crosses into a worse band. You find out from us, not from your analytics three weeks later.