Quick answer
Core Web Vitals are three measurements of real user experience: Largest Contentful Paint (loading, good is under 2.5 seconds), Interaction to Next Paint (responsiveness, good is under 200 milliseconds) and Cumulative Layout Shift (visual stability, good is under 0.1).
Largest Contentful Paint (LCP)
LCP measures how long the biggest visible element — usually the hero image or headline — takes to appear. Aim for under 2.5 seconds on mobile.
The usual culprits are oversized images, fonts that block rendering, and slow hosting. Serving modern formats such as AVIF or WebP, preloading the hero image and self-hosting fonts typically fixes it.
Interaction to Next Paint (INP)
INP measures how quickly the page responds when someone taps or clicks. Heavy JavaScript is almost always the cause. Splitting code, deferring non-critical scripts and removing unused tracking tags are the fastest wins.
Cumulative Layout Shift (CLS)
CLS measures content jumping around as the page loads — the reason people tap the wrong button. Reserve space by setting width and height on every image, avoid injecting banners above existing content, and load fonts with a matched fallback.
How to measure it honestly
PageSpeed Insights lab scores are a diagnostic, not a target. The field data section, which comes from real Chrome users, is what Google uses. Check Search Console's Core Web Vitals report monthly rather than chasing a perfect lab score.
Frequently asked questions
- Do Core Web Vitals affect rankings?
- Yes, but modestly. They act as a tiebreaker between pages of similar relevance, and they strongly affect how many visitors stay long enough to enquire.
- What is a good PageSpeed score?
- 90+ on mobile is excellent, 70–89 is acceptable for most small business sites, and below 50 usually indicates unoptimised images or excessive scripts.
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