What Are Core Web Vitals? A Plain-English Guide
Quick answer: Core Web Vitals are three scores Google uses to measure the real-world experience of your website: how fast the main content loads, how quickly the page responds when someone interacts with it, and how stable the layout is while it loads. Passing them makes your site nicer to use and gives you a small ranking edge on Google.
Key takeaways
- There are three metrics: LCP (loading), INP (responsiveness), and CLS (visual stability).
- They measure real users, not a lab test, using data from actual visits to your site.
- They are a ranking factor, part of Google's page experience signals, though content still matters most.
- Mobile is where it counts, because most sites are judged on their mobile experience.
- Passing needs 75% of visits to hit the good range for all three metrics.
The three Core Web Vitals
Each one measures a different part of how your page feels to use.
| Metric | What it measures | Good score |
|---|---|---|
| LCP (Largest Contentful Paint) | Loading: when the main content appears | 2.5 seconds or less |
| INP (Interaction to Next Paint) | Responsiveness: how fast the page reacts to a tap or click | 200 milliseconds or less |
| CLS (Cumulative Layout Shift) | Stability: how much the layout jumps as it loads | 0.1 or less |
A quick note: INP replaced an older metric called FID in 2024, so if you see FID in an old guide, INP is its modern replacement.
Why Core Web Vitals matter
Two reasons. First, they measure real frustration. A slow page, a button that does not respond, or a layout that jumps as you go to tap it all make people leave. Faster, steadier pages keep visitors and turn more of them into customers.
Second, Google uses them as a ranking signal. They will not push weak content to the top on speed alone, but when two pages are otherwise similar, the better experience wins. Good Core Web Vitals are part of a healthy technical SEO foundation.
How Google measures them
Google looks at data from real visits over the previous 28 days. A page only counts as passing when at least 75% of those visits hit the good range for all three metrics. This is why a single fast test in a tool does not tell the whole story: it is your real visitors, on real devices and connections, that decide the score.
How to check your scores
Two free tools cover it:
- PageSpeed Insights: paste in a URL for both real-world and lab results, plus specific suggestions.
- Google Search Console: its Core Web Vitals report shows which groups of pages pass or fail across your whole site.
Common problems and fixes
Most Core Web Vitals issues come down to a handful of causes:
- Slow loading (LCP): usually large images or slow hosting. Compress images, use modern formats, and choose fast hosting.
- Poor responsiveness (INP): often too much heavy JavaScript. Trim unused scripts and plugins.
- Layout jumps (CLS): usually images or ads without set dimensions. Reserve space for them so nothing shifts.
If your site is struggling, our Core Web Vitals optimisation and performance services fix these at the root. Speed is also worth weighing up when you plan a build, as our guide to website costs explains.
Frequently Asked Questions
What are the three Core Web Vitals?
They are LCP (Largest Contentful Paint), which measures loading; INP (Interaction to Next Paint), which measures responsiveness; and CLS (Cumulative Layout Shift), which measures visual stability.
What is a good Core Web Vitals score?
Aim for LCP of 2.5 seconds or less, INP of 200 milliseconds or less, and CLS of 0.1 or less. A page passes when at least 75% of real visits meet all three targets.
Do Core Web Vitals affect SEO?
Yes, they are part of Google's page experience ranking signals. They will not outrank strong content on their own, but they help you edge ahead of similar pages and keep visitors on your site.
How do I check my Core Web Vitals?
Use Google's free PageSpeed Insights for a single page or the Core Web Vitals report in Google Search Console to see how groups of pages perform across your whole site.
What replaced FID?
INP (Interaction to Next Paint) replaced FID (First Input Delay) in 2024. INP is a more complete measure of how responsive a page feels throughout a visit.
Written by WebElev8 Team
The experts at WebElev8 specialise in building fast, scalable applications and high-conversion web experiences for UK businesses. Our team shares insights on web design, modern frameworks, and SEO strategies to help small businesses thrive online.