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Core Web Vitals explained

Core Web Vitals in plain English: what LCP, INP and CLS measure, the good and poor thresholds, and the usual fixes for slow, unresponsive or shifting pages.

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LCP

Largest Contentful Paint

How long until the biggest thing on screen (usually a hero image or headline) has rendered.

Good
≤ 2.5 s Needs work
2.5 to 4 s Poor
> 4 s
Responsiveness

INP

Interaction to Next Paint

How quickly the page visibly responds to taps, clicks and key presses, across the whole visit.

Good
≤ 200 ms Needs work
200 to 500 ms Poor
> 500 ms
Visual stability

CLS

Cumulative Layout Shift

How much content jumps around unexpectedly while the page is in use.

Good
≤ 0.1 Needs work
0.1 to 0.25 Poor
> 0.25

How scores are judged

Each metric is judged at the 75th percentile of real page loads: a page passes when at least 75% of visits get a good experience. Lab tools on your own fast machine often look better than what visitors see, so measure real users.

The usual fixes

  • LCP: serve the hero image in a modern format at the right size, preload it, avoid lazy-loading it, and cut server response time (TTFB) with caching.
  • INP: break up long JavaScript tasks, defer third-party scripts, and avoid heavy work in input handlers.
  • CLS: give images, embeds and ads fixed dimensions, reserve space for banners, and use font-display with matched fallback fonts.

Also worth watching

FCP (First Contentful Paint) shows when anything first appears, and TTFB (Time to First Byte) shows how quickly your server answers. Both help explain a slow LCP.

Measure your real visitors

Privatus measures all five metrics from real visits, sampled and cookieless, next to your traffic. See performance monitoring.