What are Core Web Vitals?
Core Web Vitals are three metrics defined by Google that technically evaluate a website’s user experience: loading speed, responsiveness, and visual stability. The three Core Web Vitals are Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). Google measures them using real user data and incorporates them into the “Page Experience” ranking signal. If a page achieves a “green” rating in all three metrics, it is considered fast, responsive, and stable.
Core Web Vitals translate a vague feeling into clear numbers: Instead of “the page feels slow,” there’s a value in seconds for page load time, a value in milliseconds for response time to clicks, and a score for jerky layouts. It is precisely this measurability that makes Core Web Vitals the central KPI of technical SEO.
Brief Overview of the Term
| Characteristic | Specification |
|---|---|
| Part of speech | Noun, plural (the Core Web Vitals) |
| Pronunciation | "kor web weitels" |
| Hyphenation | Core Web Vitals |
| Number | 3 Metrics: LCP, INP, CLS |
| Related Terms | Page Experience, PageSpeed, Lighthouse, CrUX, Load Time |
What are the three Core Web Vitals?
There are exactly 3 Core Web Vitals, and each measures a different aspect of the user experience. Each metric has fixed thresholds that Google classifies as “good,” “needs improvement,” and “poor.”
- Largest Contentful Paint (LCP) – Load time. LCP measures how long it takes for the largest visible element in the viewport to load, usually an image or a headline. A value of ≤ 2.5 seconds is considered good; more than 4.0 seconds is considered poor.
- Interaction to Next Paint (INP) – Responsiveness. INP measures how quickly the page visibly responds to user input, such as clicks or taps. A value of ≤ 200 milliseconds is considered good, while more than 500 milliseconds is considered poor.
- Cumulative Layout Shift (CLS) – visual stability. CLS measures the extent to which elements shift unexpectedly during loading. The value is dimensionless. A value of ≤ 0.1 is considered good, while a value greater than 0.25 is considered poor.
A score in the yellow range (“needs improvement”) isn’t enough: Google only considers a page to have “passed” if all three Core Web Vitals are in the green range.
How are Core Web Vitals measured?
Core Web Vitals are measured in two ways: using field data and using lab data. Each method answers different questions.
- Field Data: anonymous measurements from real Chrome users, collected over 28 days as part of the Chrome User Experience Report (CrUX). This data is factored into the ranking because it reflects the actual user experience.
- Lab data: simulated measurements taken under standardized conditions, such as with Lighthouse. They are reproducible and ideal for debugging, but do not reflect real devices and networks.
The 75th percentile is key: Google doesn’t evaluate the average, but rather the value that 75% of users reach or fall below. A page is considered to meet the standard only if 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 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 measured only the delay of the very first input, not the response to subsequent clicks.
Interaction to Next Paint, on the other hand, evaluates all interactions during a session and reports the slowest one, rather than just the first interaction. INP is therefore more stringent and more closely reflects actual usability. Anyone who still has old audits based on FID should recalculate the values, because FID is no longer a Core Web Vital as of 2024.
Why are Core Web Vitals important for SEO?
Core Web Vitals are a confirmed Google ranking factor, incorporated into the “Page Experience” signal. When content is similarly relevant, the faster, more stable page may rank higher. The effect isn’t a boost, but rather a tiebreaker: Good content remains the foundation, but poor Core Web Vitals hold it back.
The second factor is conversion. Slow-loading pages and unstable layouts increase the bounce rate because users leave before the page is fully functional. Fast Core Web Vitals therefore improve two goals at once: search visibility and visitor behavior on the page. That’s why these metrics are an integral part of every technical SEO audit.
How can you improve Core Web Vitals?
Each of the three metrics has its own adjustment parameters. If you want to improve the Core Web Vitals, you should optimize each metric specifically rather than taking a one-size-fits-all approach.
- Improve LCP: Speed up server response (TTFB), use a content delivery network (CDN) and caching, serve images in modern formats such as WebP, and preload the LCP element. Important: Never use lazy loading to delay the largest image in the viewport.
- Improve INP: split up long JavaScript tasks, offload work from the main thread, remove unnecessary third-party scripts, and keep input handlers lean.
- Improving CLS: fixed width and height (or
aspect-ratio) Set up images and embeds, reserve space for ads and banners, and preload web fonts so that text doesn't wrap unexpectedly later on.
Most problems can be solved technically without altering the content. When the theme, hosting, or plugins are dragging down performance metrics, ongoing SEO support helps keep the Core Web Vitals in the green zone at all times.
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 Google’s “Page Experience” signal. Their influence is moderate and primarily serves as a tiebreaker between pages with comparable content.
What is a good LCP score?
A good LCP score is 2.5 seconds or less, measured at the 75th percentile of real users. A score between 2.5 and 4.0 seconds is considered in need of improvement, and a score above 4.0 seconds is considered poor.
Where can I view my website's Core Web Vitals?
You can find the Core Web Vitals in PageSpeed Insights, in the Core Web Vitals report in Google Search Console, and in Chrome DevTools. Search Console shows field data from real users, while PageSpeed Insights combines field and lab data.
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