What are the Core Web Vitals thresholds?

LCP is good at 2.5 seconds or under and poor above 4. CLS is good at 0.1 or under and poor above 0.25. INP is good at 200ms or under and poor above 500ms. Google applies the threshold at the 75th percentile of real visits, so a good lab score does not guarantee a good field assessment.

Why is INP showing as not measured?

Because INP can only come from real interactions by real people. There is no lab equivalent — a synthetic test has nobody clicking anything. If your site has too little traffic to appear in the Chrome UX Report, INP is genuinely unavailable, and any tool showing you one has invented it.

What happened to FID?

First Input Delay was replaced by INP in March 2024 and is no longer a Core Web Vital. It measured only the delay before processing started, which flattered pages that responded quickly and then blocked. INP measures the whole interaction through to the next paint.

Do Core Web Vitals actually affect rankings?

Yes, as part of the page experience signals, and modestly. They are a tiebreaker rather than a lever: they will not lift a weak page above a strong one, but between two comparable pages the faster one has an edge. The stronger argument is that they measure things that genuinely make people leave.

Why do lab and field numbers disagree?

A lab test is one load on one connection from one location. Field data is the 75th percentile of thousands of real visits on real devices and networks. A fast lab score with poor field data usually means your real audience is on slower hardware or connections than the test assumes.

How often should I test?

After changes that could plausibly affect loading, and then watch the field data in Search Console over the following weeks. Chasing single lab runs day to day mostly measures noise.

SEO

Core Web Vitals Test

Test LCP, CLS and INP against Google’s thresholds — on mobile and desktop, with the supporting metrics that explain them.

100% free
No sign-up

The short version

What is Core Web Vitals Test?

Core Web Vitals are three metrics Google uses to describe how a page feels to use: Largest Contentful Paint for how quickly the main content appears, Cumulative Layout Shift for how much the page moves while loading, and Interaction to Next Paint for how quickly it responds when you click. This tool runs PageSpeed against your URL and reports all three against Google's published thresholds, on mobile and desktop, alongside the supporting metrics that usually explain the result — an LCP of four seconds sitting next to a TTFB of two seconds is a server problem, not an image problem. Where a metric genuinely cannot be measured it says so instead of substituting a number.

Step by step

How to use Core Web Vitals Test

1
Enter a page
Test the specific page you care about. Vitals are measured per URL, and a template can behave very differently from the homepage.
2
Read the mobile column first
Google indexes mobile-first and the mobile thresholds are the ones that count.
3
Use the supporting metrics
TTFB explains a slow LCP. TBT usually explains a slow INP. The headline number rarely tells you what to change.
4
Re-test after each change
Lab numbers vary between runs. Look for a shift large enough to survive the noise, not a ten-millisecond improvement.

What's inside

Everything this tool
does for you

LCP, CLS and INP against the published thresholds
Mobile and desktop results
TTFB, FCP and TBT for diagnosis
Honest about unmeasurable field metrics
Free, no signup, no daily limit

Understand the result

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Questions

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What this tool does

All three Core Web Vitals in one run
Mobile and desktop side by side
Supporting metrics — TTFB, FCP, TBT — for context
Says plainly when INP cannot be measured
Free, no account, no daily limit

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