SEO glossary
Core Web Vitals
Core Web Vitals are the three metrics Google uses to measure page experience: how fast the main content appears, how quickly the page responds to input, and how much the layout shifts while loading.
The three are LCP, INP and CLS. Largest Contentful Paint should land under 2.5 seconds — the moment the biggest visible element is drawn. Interaction to Next Paint should stay under 200 milliseconds, measuring how sluggish the page feels when tapped. Cumulative Layout Shift should stay below 0.1, counting how much content jumps around under a reader's thumb.
The thresholds are assessed at the 75th percentile of real visits, which is stricter than it sounds: three quarters of your visitors have to have a good experience, not your average visitor. A fast desktop average hides a slow phone majority.
Field data comes from real Chrome users and lags by weeks, so a fix does not show up immediately. Lab tools tell you what to change; the field report tells you whether it worked, later.
Common question
- Did INP replace FID?
- Yes. Interaction to Next Paint became the responsiveness metric in March 2024, replacing First Input Delay, which only measured the first interaction.
Check this on your own site
- Site Audit
Crawl your site and group what is broken
Definitions are the easy part
The free plan opens every tool with 500 credits and no card, so you can see these numbers on your own site rather than in an example.
Start free