What Are Core Web Vitals?
Core Web Vitals are a set of three specific metrics Google uses to measure the real-world user experience of a web page. They became an official Google ranking signal in 2021 and continue to be weighted in search rankings. Pages that score well on Core Web Vitals have a measurable advantage in Google search, all else being equal.
The three Core Web Vitals are:
- LCP — Largest Contentful Paint
- CLS — Cumulative Layout Shift
- INP — Interaction to Next Paint
LCP — Largest Contentful Paint
LCP measures how long it takes for the largest visible element on the page to load. This is usually a hero image, a large heading, or a video thumbnail. It represents perceived load speed — how quickly the user sees the main content.
Good: Under 2.5 seconds
Needs improvement: 2.5–4 seconds
Poor: Over 4 seconds
How to improve LCP:
- Compress and resize hero images — use WebP format
- Remove render-blocking CSS and JavaScript
- Use a fast hosting provider with good server response times
- Add
fetchpriority="high"to your hero image tag
CLS — Cumulative Layout Shift
CLS measures how much the page layout shifts unexpectedly while loading. You have experienced high CLS when you go to click a button and it suddenly moves because an image or ad loaded above it. This is frustrating for users and penalised by Google.
Good: Under 0.1
Needs improvement: 0.1–0.25
Poor: Over 0.25
How to improve CLS:
- Always set width and height attributes on images and videos
- Reserve space for ads before they load
- Avoid inserting content above existing content dynamically
- Use CSS transform animations instead of layout-triggering properties
INP — Interaction to Next Paint
INP replaced FID (First Input Delay) in March 2024. It measures the time from a user interaction (click, tap, keyboard press) to when the browser visually responds. It captures overall interactivity throughout the entire page visit, not just the first interaction.
Good: Under 200ms
Needs improvement: 200–500ms
Poor: Over 500ms
How to improve INP:
- Reduce JavaScript execution time — break long tasks into smaller ones
- Defer non-critical JavaScript
- Remove unused JavaScript and third-party scripts
How to Check Your Core Web Vitals
Several free tools let you check your Core Web Vitals scores:
- Google Search Console — shows field data (real user data) under Core Web Vitals report
- PageSpeed Insights — shows both lab and field data for any URL
- Chrome DevTools — Lighthouse tab gives a full audit
Always prioritise fixing the pages with the most traffic first — those improvements will have the biggest impact on your overall rankings.
Core Web Vitals and SEO
Google uses Core Web Vitals as a tiebreaker — when two pages have similar relevance and authority, the page with better page experience scores will rank higher. For new sites competing against established domains, having excellent Core Web Vitals gives you an edge that many larger sites neglect. Make sure your meta tags and content are also optimised alongside your technical performance for maximum ranking potential.