Core Web Vitals are three measurements Google uses to describe how a page feels to a real visitor: how fast the main content appears, how quickly the page reacts to a tap, and how much it jumps about while loading. They are one of many signals in search ranking, and a fair description of whether a page is pleasant to use. Each has a clear threshold and a short list of usual causes.
The three numbers
| Measure | What it times | Good | Poor |
|---|---|---|---|
| LCP Largest Contentful Paint | How long until the biggest thing on the first screen, usually the main image or headline, is visible. | 2.5 s or less | over 4 s |
| INP Interaction to Next Paint | How long the page takes to visibly respond after a tap, click or key press. | 200 ms or less | over 500 ms |
| CLS Cumulative Layout Shift | How much content moves unexpectedly while the page loads. A score, not a time. | 0.1 or less | over 0.25 |
A page passes when at least three quarters of real visits fall in the "good" range for all three.
Where to see your numbers
- PageSpeed Insights. Enter an address and it shows two things: at the top, data from real visitors over the last month, if the page has enough traffic; below, a one-off test run from Google's lab, with a list of specific problems.
- Search Console. The Core Web Vitals report groups your pages into good, needs improvement and poor, using real-visitor data.
- Your browser. The Lighthouse tab in Chrome's developer tools runs the lab test on your own machine.
Lab tests and real-visitor data often disagree. The lab uses one simulated phone on one simulated connection. Real visitors use everything. When they differ, the real-visitor numbers are the ones that count; the lab test is for finding what to fix. A site with little traffic may have no real-visitor data at all, in which case the lab test is all you have.
Improving LCP: get the main content on screen sooner
Find out what the largest element is; PageSpeed Insights names it. Then, in rough order of effect:
- Make the server answer quickly. If the first response takes more than about 0.8 seconds, nothing later can make up for it. Page caching is the fix; see the traffic spike guide.
- Shrink the main image. Resize and compress it, and do not lazy-load it. The image guide covers both.
- Do not hide the main content behind scripts. A headline that only appears after a script runs, or a slider that fades in, starts late by design.
- Load fewer things first. Each stylesheet and script in the page's head delays the first paint. Remove plugins that add files to every page for a feature used on one.
Improving INP: stop the page freezing
A page feels sluggish when the browser is busy running scripts at the moment someone taps. The usual sources on a small site are other people's code:
- Chat widgets, pop-ups, social feeds and embedded players that load on every page.
- Several analytics and advertising tags running at once.
- Heavy page-builder effects and animations.
Remove what you can live without. Load the rest only when it is needed, for example a chat widget that starts when the reader clicks a button instead of on page load. Each removed script helps LCP as well.
Improving CLS: reserve the space
Layout shift happens when something arrives late and pushes other content out of the way. Give everything its space in advance:
- Images and video: always include
widthandheight. - Embeds: set a fixed height on the frame or its container.
- Advertisements: put each ad slot in a container with a minimum height matching the ad size, so the text does not jump when the ad fills in. Avoid ads that insert themselves above content the reader is already looking at.
- Banners and cookie notices: overlay them on the page, or reserve their space, instead of pushing the page down after it has drawn.
- Web fonts: a font that swaps in late can reflow whole paragraphs. Use a system font, or preload the web font and choose a fallback of similar width.
What to do first on a small site
If time is short, three changes cover most of the gain: switch on page caching, fix the main image on your most-visited pages, and remove one third-party widget. Re-test, and only then look at the finer points.
Keep it in proportion
These numbers are a tiebreaker in search, not the main event. A useful page that scores "needs improvement" will outrank an empty one that scores perfectly. Fix what is clearly poor, because it is costing you readers regardless of ranking, and do not spend weeks chasing the last few points.
Common questions
My lab score is 60 but Search Console says my pages are good. Which is right?
Both, in their own terms. Your real visitors are having a good experience, which is what matters. The lab test is harsher than most of their devices.
How long until changes show up?
The lab test reflects them at once. Real-visitor data is a rolling 28-day window, so the reports improve gradually over the following month.
Do ads make it impossible to pass?
No. They make CLS and INP harder. Reserving space for each slot and limiting the number of ad scripts is usually enough.