Core Web Vitals guide: thresholds and how to improve them

Core Web Vitals are three Google metrics that measure how fast a page loads its main content, how quickly it responds to input and how stable its layout is. A page passes when it scores "good" on all three for at least 75 percent of real visits.

This Core Web Vitals guide explains each metric, the official thresholds, and the fixes that move the numbers.

In this guide

• What Core Web Vitals are
• Core Web Vitals thresholds
• How to measure Core Web Vitals
• How to improve LCP, INP and CLS
• How Core Web Vitals affect SEO

What are Core Web Vitals?

Core Web Vitals are Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift. Together they describe loading, responsiveness and visual stability, the three parts of a page experience that users notice most.

• Largest Contentful Paint (LCP) measures when the largest image or text block in view finishes rendering.
• Interaction to Next Paint (INP) measures how quickly the page responds to clicks, taps and key presses across the whole visit. It replaced First Input Delay as a Core Web Vital in March 2024.
• Cumulative Layout Shift (CLS) measures how much visible content moves unexpectedly while the page is open.

Core Web Vitals thresholds

The Core Web Vitals thresholds are set by Google and measured at the 75th percentile of real page loads, on mobile and desktop separately.

The 75th percentile matters. A page that is fast for most visitors but slow for a quarter of them still fails.

How do you measure Core Web Vitals?

Measure Core Web Vitals with field data first, because that is what Google uses. Lab tests help you find causes, but real visits decide whether a page passes.

1. Search Console's Core Web Vitals report groups your URLs by status using real user data.
2. PageSpeed Insights shows field data for a URL when enough visits exist, plus a lab test to find causes.
3. Chrome DevTools lets you record a load or an interaction and see exactly which task blocked the page.
4. Lab metrics as proxies. Total Blocking Time in a lab test is a useful stand-in for INP while you debug.

How to improve Largest Contentful Paint

Improve LCP by making the largest element arrive and render sooner. Most slow LCP scores come from a slow server, a late-discovered image or render-blocking resources.

• Speed up the server response. A slow time to first byte delays everything after it. Caching and a CDN help most.
• Load the LCP image early. Don't lazy load it, give it a high fetch priority, and serve it in a modern format such as WebP or AVIF.
• Remove render-blocking resources. Inline critical CSS and defer scripts that are not needed for the first view.
• Size images correctly. Send images close to their display size instead of scaling large files down in the browser.

How to improve Interaction to Next Paint

Improve INP by keeping the main thread clear, so the browser can paint a response to every click quickly.

• Break up long tasks. Split work over 50 milliseconds into smaller chunks, or move it to a Web Worker.
• Give instant feedback. Show a pressed state or a spinner in the same frame as the click, before any slow work starts.
• Load heavy code on demand. Large libraries for editors, charts or file processing can load when the user first needs them.
• Trim third-party scripts. Tag managers, chat widgets and trackers often own the main thread at the worst moment.

How to improve Cumulative Layout Shift

Improve CLS by reserving space for everything before it loads, so nothing pushes content around.

• Set width and height on images and videos, or use an aspect ratio in CSS.
• Reserve space for ads, embeds and banners with a fixed minimum height.
• Avoid inserting content above existing content, such as a late cookie bar that pushes the page down.
• Use font loading strategies that limit the size jump when a web font arrives.

How do Core Web Vitals affect SEO?

Core Web Vitals are part of Google's page experience signals, which it uses in ranking, but relevance still comes first. A fast page with weak content will not outrank a helpful page that is slightly slower. Google's page experience guidance explains how these signals fit together.

Treat good scores as a baseline that protects your rankings and your visitors, not as a shortcut to the top. To see where a page loses time, run it through the Website Speed Test: it loads the page in a phone sized and a desktop browser, reports paint times, blocking time and layout shift as lab numbers, and names the heaviest files. The Website Audit saves the response timing for every URL it reads, so slow templates stand out, and the Uptime Monitor makes sure the pages are reachable in the first place.

The definitions above follow web.dev's Core Web Vitals overview.

The short version

Aim for LCP at 2.5 seconds or less, INP at 200 milliseconds or less and CLS at 0.1 or less, measured on real visits. Fix the server and the LCP image first, keep the main thread clear, and reserve space for everything that loads late. Then add these checks to your technical SEO checklist.