Core Web Vitals Explained: LCP, INP & CLS

Core Web Vitals are three metrics Google uses to measure real-world page experience, based on actual visitor data rather than lab simulations.

Largest Contentful Paint (LCP) measures loading speed — specifically, how long it takes for the largest visible element (usually a hero image or heading) to render. The passing threshold is under 2.5 seconds.

Interaction to Next Paint (INP) measures responsiveness — the time between a user’s interaction (click, tap, keypress) and the browser visually responding. It replaced the older First Input Delay (FID) metric in March 2024 because it captures every interaction on the page, not just the first. The passing threshold is under 200 milliseconds.

Cumulative Layout Shift (CLS) measures visual stability — how much content unexpectedly jumps around as a page loads (think: a button shifting right as you’re about to tap it). The passing threshold is under 0.1.

These aren’t scored from a single visit — Google evaluates them using the Chrome User Experience Report (CrUX), a rolling 28-day dataset of real Chrome users, at the 75th percentile. That means at least 75% of your visits need a “good” score for a page to pass.

INP is currently the hardest of the three metrics for most sites to pass, since fixing it usually requires reducing heavy JavaScript execution rather than a quick settings change.