Core Web Vitals explained for business owners
Core Web Vitals are three measurements Google uses to judge how a page feels to use: how fast the main content appears, how quickly it responds to a tap and how much it jumps around while loading. Here's what each means and what usually fixes it.
The three measurements
| Measurement | What it means | Good |
|---|---|---|
| Largest Contentful Paint (LCP) | Time until the biggest thing on screen, usually the main photo or heading, has appeared | 2.5 seconds or less |
| Interaction to Next Paint (INP) | How quickly the page visibly reacts when someone taps or types | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | How much the content moves around unexpectedly while the page loads | 0.1 or less |
Lab data and field data
PageSpeed Insights shows two kinds of result. The lab result is a test run on the spot, on a simulated phone, and gives the familiar score out of 100. The field result, when it appears, comes from real Chrome users who visited your site over the past 28 days. Google uses field data for search. Many small sites don't get enough visits to have field data, so the lab test is the best guide.
The lab score moves by a few points between runs. Don't chase a number; fix the problems listed underneath it.
Fixing LCP
- Resize and compress the main image, and use WebP or AVIF
- Don't lazy-load the image at the top of the page
- Remove sliders and background videos from the first screen
- Cut render-blocking scripts and styles, and use caching or a CDN
Fixing INP
- Remove scripts nobody uses, especially third-party widgets
- Delay chat widgets and similar tools until they're needed
- Avoid heavy page builders that run lots of code on every tap
Fixing CLS
- Give every image and video a width and height so space is reserved
- Don't insert banners or pop-ups above content after it has loaded
- Load fonts so text doesn't jump when they arrive
Do they affect rankings?
They're part of how Google assesses page experience, but relevance and quality matter far more. A slow page that answers the search well can still rank. The bigger reason to care is people: a page that appears quickly and doesn't jump keeps more visitors reading and contacting you. For the most common causes of slowness, read why is my website slow, or see my speed optimisation service.