Core Web Vitals are three measurements Google uses to judge real-world page experience. Largest Contentful Paint (LCP) measures loading speed and should be 2.5 seconds or less. Interaction to Next Paint (INP) measures how quickly a page responds to taps and clicks and should be 200 milliseconds or less. Cumulative Layout Shift (CLS) measures visual stability and should be 0.1 or less. Google assesses each at the 75th percentile of real visits, and they form part of the page experience signals used in ranking.
Why Core Web Vitals matter
Slow, jumpy pages frustrate visitors. People leave before the page loads, tap the wrong button when content moves, or give up when a form does not respond. For a business, that means lost enquiries and wasted ad spend.
Google includes Core Web Vitals in its page experience signals. They are not the strongest ranking factor; relevant, helpful content matters more. But when competing pages are similarly useful, a faster and more stable experience can help, and it improves conversion rates regardless of rankings.
Largest Contentful Paint (LCP): loading
LCP measures how long it takes for the largest visible element, usually a hero image, banner or main heading, to appear on screen. It reflects when a visitor feels the page has loaded.
- Good: up to 2.5 seconds.
- Needs improvement: up to 4 seconds.
- Poor: more than 4 seconds.
Common causes of slow LCP include large uncompressed images, slow hosting, render-blocking CSS and JavaScript, and hero images that load late because they are set as backgrounds or lazy-loaded.
Interaction to Next Paint (INP): responsiveness
INP measures the delay between a user interaction, such as a click, tap or key press, and the next visual update on screen. It replaced First Input Delay as a Core Web Vital in March 2024 because it considers all interactions during a visit, not just the first one.
- Good: up to 200 milliseconds.
- Needs improvement: up to 500 milliseconds.
- Poor: more than 500 milliseconds.
Poor INP usually comes from heavy JavaScript: large page builders, too many third-party scripts such as chat widgets and trackers, or complex code running when buttons are pressed.
Cumulative Layout Shift (CLS): visual stability
CLS measures how much visible content moves unexpectedly while the page loads. Everyone has experienced it: you go to tap a link and an advert pushes it down.
- Good: a score no higher than 0.1
- Needs improvement: a score up to 0.25
- Poor: anything above 0.25
Layout shifts are typically caused by images and videos without width and height set, adverts or embeds that load without reserved space, cookie banners inserted above content, and web fonts that change text size when they load.
How to measure your Core Web Vitals
There are two kinds of data. Field data comes from real Chrome users through the Chrome User Experience Report, and it is what Google uses for page experience. Lab data comes from a simulated test and is useful for diagnosing problems.
- PageSpeed Insights: shows field data for the page and site when enough traffic exists, plus a Lighthouse lab test with suggestions.
- Google Search Console: the Core Web Vitals report groups your URLs into good, needs improvement and poor for mobile and desktop.
- Chrome DevTools: the Performance panel helps developers find exactly which element or script causes a problem.
Low-traffic sites may not have field data. In that case, use lab tests as a guide, and test on a mid-range Android phone over mobile data, since that reflects many real visitors in India.
How to improve each metric
Improving LCP
- Compress images and serve modern formats such as WebP or AVIF at the right size.
- Do not lazy-load the main hero image, and preload it if needed.
- Use good hosting, server caching and a content delivery network.
- Reduce render-blocking CSS and defer non-essential JavaScript.
Improving INP
- Remove plugins and third-party scripts you do not need.
- Load chat widgets and trackers after the page becomes interactive.
- Break up long JavaScript tasks so the browser can respond between them.
Improving CLS
- Set width and height attributes, or aspect ratios, on all images and videos.
- Reserve space for adverts, embeds and banners before they load.
- Use font-display settings and matched fallback fonts to limit text reflow.
Common misunderstandings
- A Lighthouse score of 100 is not the goal; passing field data for real users is.
- Core Web Vitals do not outweigh relevance. A fast page with weak content will not outrank a helpful one.
- Changes take time to appear, since field data is collected over a rolling 28-day period.
- Desktop and mobile are assessed separately, and mobile usually needs more work.
Frequently asked questions
Do Core Web Vitals affect Google Ads?
They are not part of Ads auctions directly, but landing page experience affects ad quality and conversion rates, so a faster page usually improves campaign efficiency.
Can WordPress sites pass Core Web Vitals?
Yes. A lightweight theme, fewer plugins, optimised images, caching and good hosting are usually enough for most business sites.
How often should I check them?
Review the Search Console report monthly, and test key pages after redesigns, new plugins or new tracking scripts.
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