Core Web Vitals in plain words

Core Web Vitals are three measurements Google uses to describe how a page feels to the person visiting it: whether it shows up quickly, whether it answers when you tap it, and whether the text stays still while you read. They are Google’s metrics, measured in real visitors’ browsers, and they feed into what Google calls page experience. They are not a grade for the server.

The three, without the acronyms

Metric In plain words Usual cause Where to start
LCP (Largest Contentful Paint) How long the biggest visible thing takes to appear: usually the image or headline at the top. A large or deferred top image; a slow server response; blocking CSS. Shrink and convert the image; see WebP; switch on page caching.
INP (Interaction to Next Paint) How long the page takes to react to a tap or click. It replaced FID. Lots of JavaScript, especially third-party: chat widgets, ads, trackers. Remove scripts nobody uses; defer the rest.
CLS (Cumulative Layout Shift) How much the content jumps around while it loads. Images without width and height; ads and banners that push text down; fonts that swap. Give images dimensions and reserve space for what loads later.

How to see yours, step by step

1 Open PageSpeed Insights (from Google), paste the page address and pick the mobile tab, which is where most sites fail first.
2 Tell the two kinds of data apart. The top panel, when there is one, shows field data: real visitors over recent weeks. The panel below is a lab test, run now, on a simulated phone. They serve different purposes.
3 See which of the three fails and read the list of opportunities the tool offers for that one. Fix the biggest, one at a time.
4 For the whole site, use the “Core Web Vitals” report in Search Console, which groups pages by problem. It only appears when the site has enough visits for Google to hold data.
5 Measure again after each change, but remember: field data reflects the last few weeks of visits, so it is slow to move. The lab test answers straight away.
The 0 to 100 score is not Core Web Vitals. The big number in PageSpeed is a lab score; Core Web Vitals are the three metrics above. Chasing 100 eats time and can break the site. The limits Google counts as “good” and “poor” are published by Google on web.dev, and they change: check them there instead of memorising them.
What weighs on it Does the server matter?
Large images in heavy formats No: it is content. It sits on your side.
Third-party scripts (chat, ads, trackers) No: they load from other places.
Time to the first byte of the page Partly: it depends on whether the page comes from cache or is built again. See LiteSpeed Cache.
Heavy plugins and themes In part: the server only does what the code asks of it.
Useful content still counts for more. Google itself says a good page experience does not replace relevant content. Use these metrics to remove friction, not as a goal in themselves. And if the site is fast for you and slow for everyone else, the problem lies elsewhere: fast for you, slow for everyone else.

Got a Google report you cannot make sense of? Send us the page address and what the tool says, and we will explain what belongs to the server and what belongs to the site.

Open a support ticket

SEE ALSO

Measuring your site speed: which tools, and what the numbers mean

Image optimisation and WebP

The site is slow: what to measure before you change plan

RECOMMENDED PRODUCT

Web hosting with cPanel

Domain and SSL included, daily backups and the panel you already know. from KSh858.00/mo (3-year plan, with coupon)

See plans
  • 0 Users Found This Useful
Was this answer helpful?

Related Articles

How to monitor your site performance in cPanel cPanel keeps a record of everything that happens on your hosting - who visited, how much traffic you used, which errors...
The site is slow: what actually makes a difference «The site is slow» means different things depending on who says it: the first page takes ages to appear, the admin panel...
Cloudflare: when it helps, how to switch it on, and the cache that fools you Cloudflare sits in front of your site: visitors reach it first, and it comes to us for what it needs. That brings three...
The site is slow: what to measure before you change plan «The site is slow, I think I need a bigger plan.» It is one of the messages we get most, and most of the time the bigger...
What a CDN is, and when it makes a difference (and when it does not) A CDN (content delivery network) is a set of machines spread around the world that keep copies of your site and hand the...
Browser caching with .htaccess Browser caching is the kind that lives on the visitor’s own computer: if the logo, the CSS and the JavaScript arrive wit...