Core Web Vitals are three numbers Google uses to describe how a page feels to a real person on a real phone. They have awkward names, but each one is a plain complaint you have had yourself about somebody else's website.
The three, in plain words
Largest Contentful Paint is how long until the main thing on screen, usually your hero photo or heading, has actually appeared. Google's threshold for good is 2.5 seconds or less.
Interaction to Next Paint is how long the page takes to visibly respond when somebody taps something. Good is 200 milliseconds or less.
Cumulative Layout Shift is how much the page jumps about while it loads. Good is 0.1 or less. The thresholds are set out on web.dev, which is Google's own site for this.
A worked example
A paving firm's site had a fine looking gallery. On a phone, the photos loaded without any space reserved for them, so every time one arrived the text shoved down the screen.
A homeowner reaching for the phone number tapped the gallery instead because the button had moved under their thumb. That is layout shift, and it is the one customers complain about without knowing the name for it. Reserving the space by putting a width and height on every image fixed it in an afternoon.
How to see yours
PageSpeed Insights shows the lab numbers for any address, and Google Search Console reports the real world figures from actual visitors once your site has enough traffic. The real world ones are the ones that count, because they come from phones like your customers' rather than from a test machine.
Why it matters for your site
Check these on your own site
- Slow first paint means people leave before they see your work.
- A page that jumps about causes wrong taps, and a wrong tap is a lost call.
- Every image needs a width and height set, so its space is reserved before it arrives.
- Check the mobile numbers. Desktop results flatter almost every site.
- These are experience measures first and ranking factors second. Fixing them helps the customer either way.
Common questions
What counts as good Core Web Vitals?
Google's thresholds are 2.5 seconds or less for Largest Contentful Paint, 200 milliseconds or less for Interaction to Next Paint, and 0.1 or less for Cumulative Layout Shift.
Do Core Web Vitals affect my ranking?
They are part of how Google assesses page experience, but content and relevance matter far more. Fix them because they make the page usable, not because of the ranking alone.