Core Web Vitals are three measurements from Google of how a page feels to real users: how fast the main content appears (LCP), how quickly the page responds (INP) and how stable the layout stays (CLS). Good means LCP within 2.5 seconds, INP within 200 milliseconds and CLS of 0.1 or less.
What do the three metrics measure?
They measure loading, responsiveness and visual stability. Google publishes the definitions and targets on web.dev, and judges each at the 75th percentile of page loads, separately for mobile and desktop. In practice: at least three out of four visits should reach the target.
| Metric | What it means | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP, Largest Contentful Paint | When the largest image or text block is shown | 2.5 s or less | Up to 4 s | Over 4 s |
| INP, Interaction to Next Paint | How fast the page responds to clicks, taps and keys | 200 ms or less | Up to 500 ms | Over 500 ms |
| CLS, Cumulative Layout Shift | How much the layout jumps unexpectedly | 0.1 or less | Up to 0.25 | Over 0.25 |
INP became a stable Core Web Vital in 2024, replacing an older metric called FID. Articles that still mention FID are out of date.
Do Core Web Vitals affect rankings?
They're part of the picture, not the deciding factor. Google says it highly recommends achieving good scores for success with Search, and that this aligns with what its core ranking systems seek to reward, along with other aspects of page experience. It also advises against fixating on one or two aspects. A fast page with weak content won't win on speed, and nobody can promise you a ranking from better scores.
How do you check your own site?
- Run [PageSpeed Insights](https://pagespeed.web.dev/) on your homepage and main templates.
- Read the top section first. That's field data: real Chrome users over the previous 28 days.
- Use the lab score for debugging. It's one simulated load, so it can differ from the field data.
- Open the Core Web Vitals report in Search Console to see groups of pages across your whole site.
Small sites often have too little traffic for field data. PageSpeed Insights then falls back to your whole domain or shows no real-user data at all. In that case, use the lab result as a guide and test on a real phone yourself.
What usually causes poor scores?
| Metric | Common causes | First thing to try |
|---|---|---|
| LCP | Slow server, a large or late-loading main image, blocking scripts | Compress the main image and don't lazy-load it |
| INP | Long tasks and heavy scripts | Remove scripts you no longer use |
| CLS | Images and embeds without dimensions, injected content, web fonts | Reserve space for images, ads and embeds |
A practical habit: look at what was added after launch first. Tracking tags, chat widgets and cookie tools build up over time and rarely get removed. Ask of each one who still uses it.
When should you stop worrying?
Stop when your main templates are in the good range for real users. Chasing a perfect lab score of 100 beyond that is rarely the best use of your time. Spend it on what you say instead: what makes a good website goes through the rest. Do worry when your poor pages are the ones that bring in customers, or when scores fall after a change.
Check again after every redesign, which is why they're on our redesign checklist. A Website Care plan, €99 a month excluding VAT, includes monitoring and basic checks if you want someone else to watch it. If a poor score comes from the base of the site, see redesign or rebuild.
