Quick answer
Core Web Vitals are three Google metrics for real-user experience: Largest Contentful Paint (LCP) measures loading, Interaction to Next Paint (INP) measures responsiveness, and Cumulative Layout Shift (CLS) measures visual stability. A page passes when, at the 75th percentile of visits, LCP is 2.5 seconds or less, INP is 200 milliseconds or less, and CLS is 0.1 or less.
- INP replaced First Input Delay (FID) as a Core Web Vital in March 2024.
- Google ranking systems use Core Web Vitals, but relevance and helpfulness come first.
- Field data from real users is what counts; lab tools help you diagnose.
- Mobile and desktop are measured separately.
What are the three Core Web Vitals?
| Metric | What it measures | Good | Poor |
|---|---|---|---|
| LCP: Largest Contentful Paint | Time until the largest image or text block is visible | 2.5 s or less | More than 4 s |
| INP: Interaction to Next Paint | Delay between a tap, click, or key press and the screen updating | 200 ms or less | More than 500 ms |
| CLS: Cumulative Layout Shift | How much the layout moves unexpectedly while loading | 0.1 or less | More than 0.25 |
How do you test Core Web Vitals?
- Search Console Core Web Vitals report
- Groups of URLs that pass, need improvement, or are poor, from real-user data.
- PageSpeed Insights
- Field data for a URL or origin, plus a lab test with specific suggestions.
- Lighthouse and browser DevTools
- Lab testing to find the cause of a problem while you develop.
How do you improve LCP?
- Serve the main image in a modern format, sized for the device
- Do not lazy-load the hero image; preload it if it is discovered late
- Reduce server response time with caching and a CDN
- Remove render-blocking CSS and JavaScript from the critical path
- Use prerendered or server-rendered HTML so content does not wait for JavaScript
How do you improve INP?
- Break up long JavaScript tasks so the browser can respond
- Remove or defer third-party scripts that are not essential
- Avoid heavy work in click and input handlers; update the screen first
- Reduce the size and complexity of the page structure
How do you improve CLS?
- Set width and height, or an aspect ratio, on images and videos
- Reserve space for ads, embeds, and banners
- Load web fonts so text does not jump when they arrive
- Do not insert content above existing content after load
Do Core Web Vitals affect SEO?
Google says its ranking systems use Core Web Vitals as part of page experience, and recommends good Core Web Vitals for success with Search. It also says great page experience does not override having the most relevant, helpful content. Treat speed as a foundation: it rarely wins on its own, but slow pages lose visitors and enquiries.
Speed and Core Web Vitals with Hudace
Every Hudace website is built and tested for Core Web Vitals on mobile before launch. For existing sites, our technical SEO team finds and fixes what slows your pages. Check your site with the free website grader or talk to us.
Frequently asked questions
What are the Core Web Vitals?
Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness), and Cumulative Layout Shift (visual stability).
What is a good LCP score?
2.5 seconds or less at the 75th percentile of page visits.
What replaced FID?
Interaction to Next Paint (INP) replaced First Input Delay as a Core Web Vital in March 2024.
Why do PageSpeed Insights and Search Console show different results?
The lab test simulates one load on set hardware; field data reflects real users over the previous 28 days. Field data is what Google uses.
Do Core Web Vitals affect rankings?
Google ranking systems use them as part of page experience, but relevance and helpful content matter more.
How long until improvements show in Search Console?
Field data covers a rolling 28-day period, so improvements appear gradually over about four weeks.
Which is the hardest Core Web Vital to fix?
INP is often hardest on JavaScript-heavy sites, because fixes involve how scripts run rather than file sizes.