Core Web Vitals — Google's new page experience signals
Google has announced three new metrics that will become a ranking signal: Largest Contentful Paint, First Input Delay and Cumulative Layout Shift. Here is what each one measures and how to think about it.
Tom BarberLast month Google announced something it is calling "Core Web Vitals" — three new metrics that, from sometime next year, will become part of how Google decides who ranks. The metrics themselves are not new (Google has been hinting at them for years), but combining them into a single ranking signal is a step change.
The three metrics
- Largest Contentful Paint (LCP): how long it takes for the biggest visible element on the page — usually the hero image or main headline — to appear. Google's target is under 2.5 seconds.
- First Input Delay (FID): how long it takes the page to respond when a user first interacts with it — clicking a button, opening a menu. Target: under 100 milliseconds.
- Cumulative Layout Shift (CLS): how much the page jumps around as it loads. Anyone who has tried to tap a button only for an ad to load and shove the page down has experienced bad CLS. Target: under 0.1.
Why it matters
Page speed has been a ranking factor for years, but the signal was crude — essentially a single overall time. Core Web Vitals is more nuanced. It measures the user-felt experience of loading and interacting with a page, not just the raw seconds. A page that loads its main content quickly, responds instantly to clicks, and does not jump about feels good to use, and Google now has measurable proxies for "feels good".
What to do about it
Google has made the metrics available everywhere it can — in Search Console, in PageSpeed Insights, in the Chrome DevTools Lighthouse tab, and in the Chrome extension itself. Run your most important pages through PageSpeed Insights and look at the Field Data section. That is what Google sees from real users.
The biggest wins for most sites tend to be lazy-loading images below the fold, deferring third-party scripts (chat widgets, tracking pixels, ad code), and reserving space for images and embeds in CSS so they do not push content around as they load. None of it is rocket science, but it benefits from doing it methodically.
Core Web Vitals will not start affecting rankings until sometime in 2021, so there is time. But the metrics also correlate strongly with conversion rate, so they are worth doing for that reason alone.