A fast website: the 3 metrics Google actually looks at

A slow website loses visitors before they’ve read a single line. Google knows this: for several years now, it has measured your visitors’ real experience with three metrics, the Core Web Vitals. They aren’t the whole of SEO, but when content is equal, the website that’s easier to use has the edge.

Here is what they measure, the thresholds to aim for and what I set up on every website.

1. LCP: displaying the main content

Largest Contentful Paint measures how long it takes to display the largest visible element: often the image or the heading at the top of the page.

Target: under 2.5 seconds.

What improves it:

• images in the right format (WebP or AVIF) and at the right size for each screen;
• the top-of-page image loaded first, the others only as you get close to them;
• responsive hosting and few scripts blocking the page load.

2. INP: responsiveness to interactions

Interaction to Next Paint measures the delay between an action (a click, a key press) and the visible response on screen.

Target: under 200 milliseconds.

What improves it:

• less JavaScript, and above all fewer third-party scripts (widgets, trackers, chats) loaded on every page;
• animations that rely on what the browser handles efficiently, rather than heavy calculations on every frame.

3. CLS: layout stability

Cumulative Layout Shift measures visual shifts during loading: the button that jumps just as you click, the text that moves down when an image arrives.

Target: under 0.1.

What improves it:

• reserved dimensions for every image and every video;
• fonts loaded properly, so text doesn’t change size along the way;
• no banner or block injected above the content after the fact.

How to measure your website

• PageSpeed Insights (pagespeed.web.dev): enter your address, look first at the “real-world data” section if there is one, then at the recommendations.
• Google Search Console, “Core Web Vitals” report: the list of pages to fix, grouped by issue.

Always test the mobile version: it’s the most demanding, and it’s the one Google uses first.

My takeaway

A fast website can’t be fixed at the end: it’s decided at the mockup stage (number of elements, image weight, choice of animations) and checked at every step. That’s why I measure the performance of every website before it goes live.

Want to know where yours stands? Write to me and I’ll send you a diagnosis with the priority fixes.