Google uses three “Core Web Vitals” to judge how a page performs for real users. They matter because they’re part of how Google ranks pages, and because they measure actual clicking-and-scrolling humans, not lab tests.
LCP — Largest Contentful Paint (the hero image)
LCP is how long it takes the biggest visible element — usually a hero image or headline — to appear. You want it under 2.5 seconds.
What makes it slow, in order of how often we see it:
- Massive unoptimized images
- Render-blocking scripts and stylesheets
- Slow server responses and time to first byte (TTFB)
Fix it with image optimization, preloading the hero image, and caching.
INP — Interaction to Next Paint (the clicks and taps)
INP measures how quickly the page responds to a click or tap. If you click a button and nothing happens for a second, that’s a bad INP. Target: under 200ms.
The usual culprits are heavy third-party scripts (chat widgets, trackers) and JavaScript running on the main thread when the user tries to interact. Remove what you don’t need, defer the rest.
CLS — Cumulative Layout Shift (the layout jumping)
CLS measures how much the page layout shifts after load — images popping in, banners appearing, fonts reflowing. Target: under 0.1.
Fixes are mostly CSS hygiene: reserve space for images and embeds, load fonts responsibly, and don’t inject banners that push content down.
Great, but how do I measure it?
- Lighthouse for a fast lab snapshot
- PageSpeed Insights for field data from real Chrome users
- CrUX for your actual traffic performance
- Search Console’s Core Web Vitals report for pages Google sees
Do you need all three green?
Google’s rule is that all three should pass at the 75th percentile of users. Missing any one of them can cost you ranking headroom. It’s not just SEO though — every study finds faster pages convert better.
If you’d rather not debug render-blocking yourself, that’s exactly the kind of work we do. Run a free audit and we’ll tell you which of the three is dragging you down — and how to fix it.