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·By GretTech Team·4 min read

Core Web Vitals Explained for Business Owners

Core Web Vitals Explained for Business Owners: cover image with the article title

Core Web Vitals are three measurements Google uses to judge how a page feels to use: how quickly the main content appears, how fast the page responds when you tap something, and whether things jump around while it loads. They're part of how Google assesses page experience, and more directly, they reflect whether visitors stay or leave.

You don't need to be technical to understand them. Here's what each one means, what counts as good, and what usually fixes a poor score.

The three measurements

Largest Contentful Paint (LCP): does the main content load quickly?

LCP measures how long it takes for the largest thing on the screen, usually a hero image or a big heading, to appear. It's a good stand-in for "when does the page look ready?"

Good: 2.5 seconds or less.

Common causes of a poor score: large, uncompressed images; slow hosting; heavy fonts or scripts that block the page from showing; the main image being loaded late.

Interaction to Next Paint (INP): does the page respond quickly?

INP measures how long the page takes to respond visibly after someone taps, clicks or types, across the whole visit. It replaced an older measure, First Input Delay, in 2024.

Good: 200 milliseconds or less.

Common causes of a poor score: too much JavaScript running at once, often from third-party scripts such as chat widgets, trackers and ad tags; complicated pages doing a lot of work on each click.

Cumulative Layout Shift (CLS): does the page stay still?

CLS measures how much content moves around unexpectedly while the page loads. You've seen it: you go to tap a button and an image loads above it, pushing it down.

Good: 0.1 or less.

Common causes of a poor score: images and videos without set dimensions; banners, cookie notices or ads that appear above the content; fonts that change size as they load.

How Google measures them

Google uses real visits from Chrome users rather than a lab test. For each measurement, it looks at the experience of the slowest quarter of visits: a page passes if at least 75% of visits are in the good range. That's why your own fast laptop on office Wi-Fi isn't a fair test; many visitors are on mid-range phones and mobile data.

How to check your site

  • PageSpeed Insights (pagespeed.web.dev): enter a URL to see real-visitor data if Google has enough of it, plus a lab test with suggestions.
  • Google Search Console: the Core Web Vitals report groups your pages into good, needs improvement and poor, for mobile and desktop separately.
  • Lighthouse, built into Chrome's developer tools, for testing changes before they go live.

Start with the mobile results. They're usually worse, and most visitors are on phones.

The fixes that help most often

  1. Compress and resize images. Serve modern formats such as WebP or AVIF, at the size they're actually shown. This is the most common single fix for LCP.
  2. Load the main image first and lazy-load the images further down the page.
  3. Set dimensions on images, videos and embeds so the browser reserves space for them. This fixes most CLS problems.
  4. Cut third-party scripts. Each chat widget, tracker and tag costs time. Remove the ones you don't use and load the rest after the page is ready.
  5. Use a good host and pre-built pages where possible, so the server responds quickly.
  6. Load fonts sensibly: fewer weights, and hosted with the site rather than fetched from elsewhere.

How much does it matter for SEO?

Good Core Web Vitals won't lift a page with weak content above better pages. Relevance and usefulness come first. But between pages of similar quality, the faster, steadier one has an edge, and visitors are much more likely to stay on it. The bigger benefit is often in what happens after people arrive: more of them read on, get in touch or buy.

Where to go from here

If your scores are poor, start with images and third-party scripts; they're behind most problems. If the site is built on a heavy theme or platform, fixing speed can be harder, and our Next.js and WordPress comparison covers why the platform matters.

We check every page we build against these measurements before launch, and keep an eye on them as part of ongoing support. If your site is slow and you're not sure why, we can take a look; here's how we approach web development.

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