Core Web Vitals

Google's three scores that measure the real experience of using your site

📖 Detailed description

Core Web Vitals are a set of three metrics Google uses to measure the real user experience on your site. This is not dry "speed" - it answers the questions: how fast does the content appear, how quickly does the page respond to a tap, and do elements jump around under the user's finger?

LCP (Largest Contentful Paint) measures how long it takes for the largest visible element (usually a big image or heading) to load. Target: under 2.5 seconds. INP (Interaction to Next Paint) - which replaced the old FID in 2024 - checks how fast the page responds to user actions (clicks, taps). Target: under 200 ms. CLS (Cumulative Layout Shift) measures layout stability - whether buttons and text move around while the page loads. Target: under 0.1.

Core Web Vitals are an official ranking factor (Page Experience). Poor scores mean not only a lower position, but above all frustrated users who hit the "back" button. Run a basic measurement in the /core-web-vitals tool.

Most common problems

High LCP

The main content loads too slowly - the user stares at a blank screen

High INP

The page lags after a click and responds with a delay

High CLS

Elements jump around while loading, so you tap the wrong thing

Heavy JavaScript

Large scripts block the main thread and hurt interactivity

How to fix it?

Optimize and compress your largest images, use modern formats (WebP/AVIF)

Reserve space for images and ads (width/height) so the layout does not shift (CLS)

Reduce and defer unnecessary JavaScript - it improves INP

Load critical CSS early and lazy-load the rest of your resources

Test with real-world data (CrUX field data), not just in the lab

Examples

Good example

LCP 1.9s • INP 120ms • CLS 0.05 - all three in the green zone

Bad example

LCP 6s • INP 500ms • CLS 0.4 - users leave before the page loads

🔗 Related indicators

📱

Mobile friendliness

Does your site work well on a phone? That is how most people view it!

🤖

Robots.txt and Sitemap

A map and a set of instructions telling Google how to navigate your site

🔗

Canonical URLs

Which address is the "official" one when the same content lives at several URLs

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