What are Core Web Vitals?

Core Web Vitals are three metrics defined by Google that rate the user experience of a web page in technical terms: loading speed, responsiveness and visual stability. The three Core Web Vitals are called Largest Contentful Paint (LCP), Interaction to Next Paint (INP) and Cumulative Layout Shift (CLS). Google measures them on data from real users and uses them as part of the “Page Experience” ranking signal. A page that lands in the green range on all three values counts as fast, usable and stable.

Core Web Vitals turn a vague impression into clear numbers: instead of “the page feels slow” you get a value in seconds for the page build, a value in milliseconds for the reaction to a click and a score for jumpy layouts. That measurability is what makes the Core Web Vitals the central KPI on the technical side of SEO.

Core Web Vitals at a glance

What are the three Core Web Vitals?

There are exactly 3 Core Web Vitals, and each one measures a different dimension of the user experience. Every metric has fixed thresholds that Google splits into “good”, “needs improvement” and “poor”.

1. Largest Contentful Paint (LCP), load time. LCP measures how long it takes until the largest visible element in the viewport has loaded, usually an image or a heading. Good is a value of 2.5 seconds or less, poor is anything above 4.0 seconds.
2. Interaction to Next Paint (INP), responsiveness. INP measures how quickly the page reacts visibly to input such as a click or a tap. Good is a value of 200 milliseconds or less, poor is anything above 500 milliseconds.
3. Cumulative Layout Shift (CLS), visual stability. CLS measures how much elements move around unexpectedly while the page loads. The value has no unit. Good is a value of 0.1 or less, poor is anything above 0.25.

A value in the yellow range (“needs improvement”) is not enough: Google only counts a page as passed once all three Core Web Vitals sit in the green range.

How are Core Web Vitals measured?

Core Web Vitals are measured in two ways, with field data and with lab data. Each answers a different question.

• Field data: anonymous measurements from real Chrome users, collected in the Chrome User Experience Report (CrUX) over 28 days. This is the data that feeds into ranking, because it reflects the real experience.
• Lab data: simulated measurements under standardized conditions, for example with Lighthouse. They are reproducible and ideal for debugging, but they do not mirror real devices and networks.

What counts is the 75th percentile: Google does not rate the average, it rates the value that 75 % of users reach or beat. A page only passes when three out of four visitors have a good experience. The most important tools are PageSpeed Insights, the Core Web Vitals report in Google Search Console and the Chrome DevTools.

What happened to FID?

INP has replaced FID. Until March 12, 2024, First Input Delay (FID) was the third Core Web Vitals metric for interactivity. FID only measured the delay of the very first input, not the reaction to later clicks.

Interaction to Next Paint rates all interactions in a session instead and reports the slowest one, rather than just the first contact. That makes INP stricter and closer to how usable a page really is. If you still have older audits with FID in them, collect the values again, because FID has not been a Core Web Vital since 2024.

Why do Core Web Vitals matter for SEO?

Core Web Vitals are a confirmed Google ranking factor, embedded in the “Page Experience” signal. When two pages are similarly relevant, the faster and more stable one can rank better. The effect is not a turbo, it works as a tiebreaker: good content stays the foundation, but weak Core Web Vitals slow it down.

The second lever is conversion. Slow pages and jumping layouts push the bounce rate up, because people give up before the page becomes usable. Fast Core Web Vitals therefore serve two goals at once: visibility in search and the behavior of visitors on the page. That is why these values are a fixed part of every technical SEO audit.

How do you improve the Core Web Vitals?

Each of the three metrics has its own levers. If you want to improve your Core Web Vitals, work on one value at a time instead of optimizing everything at once.

• Improve LCP: speed up the server response (TTFB), put a content delivery network (CDN) and a cache in place, serve images in modern image formats such as WebP and preload the LCP element. One rule: never delay the largest image in the viewport with lazy loading.
• Improve INP: break up long JavaScript tasks, take work off the main thread, remove unnecessary third-party scripts and keep input handlers lean.
• Improve CLS: set a fixed width and height (or aspect-ratio) for images and embeds, reserve space for ads and banners, and preload web fonts so that text does not reflow afterwards.

Most of these problems can be solved on the technical level without touching the content. Where a theme, the hosting or a plugin drags the values down, ongoing SEO services keep the Core Web Vitals in the green range for good.

Frequently asked questions about Core Web Vitals

How many Core Web Vitals are there?
There are 3 Core Web Vitals: Largest Contentful Paint (LCP) for load time, Interaction to Next Paint (INP) for responsiveness and Cumulative Layout Shift (CLS) for visual stability.

Are Core Web Vitals a ranking factor?
Yes, Core Web Vitals are part of the Google “Page Experience” signal. The influence is moderate and works above all as a tiebreaker between pages with comparable content.

What is a good LCP value?
A good LCP value is 2.5 seconds or below, measured at the 75th percentile of real users. Between 2.5 and 4.0 seconds the value counts as needing improvement, above 4.0 seconds as poor.

Where do I see the Core Web Vitals of my website?
You find the Core Web Vitals in PageSpeed Insights, in the Core Web Vitals report of Google Search Console and in the Chrome DevTools. Search Console shows field data from real users, PageSpeed Insights combines field and lab data.