Core Web Vitals in 2026: a practical checklist.

Core Web Vitals are the metrics Google uses to understand how fast and stable your pages feel to real visitors. They are not a vague performance score. They measure three specific things: how quickly the main content appears, how responsive the page is to interaction, and how stable the layout stays while loading. Getting them right improves both rankings and the experience for the people who actually use your site.

The three metrics

Largest Contentful Paint (LCP)

LCP measures when the largest visible element — usually an image or a headline — finishes loading. If that takes too long, the page feels slow even if everything else loads instantly. Slow servers, heavy images and render-blocking scripts are the usual causes. A good LCP is roughly 2.5 seconds or faster on a typical connection.

Interaction to Next Paint (INP)

INP measures how quickly the page responds when a visitor clicks or taps. A page can load fast but still feel sluggish if clicks trigger long delays. Long-running scripts and heavy JavaScript are the usual culprits. INP replaced the older First Input Delay metric, and it is a better reflection of how a page feels during real use.

Cumulative Layout Shift (CLS)

CLS measures unexpected movement while a page loads. If images, ads or embeds push content around as they load, the page is hard to use — a visitor taps a button and it moves. Reserving space for images and avoiding inserting content above existing content are the main fixes. A low CLS means the layout stays put.

How to measure

You do not need to guess at any of this. PageSpeed Insights, the Chrome user report and field data in Search Console all report your actual scores. The key is to look at field data — measurements from real visitors — alongside lab tests, because what happens on real devices and connections is what matters most.

Where to look

• PageSpeed Insights for per-page lab and field scores.
• Search Console Core Web Vitals report for site-wide field data.
• The Chrome User Experience Report for aggregate data by page and origin.

A practical checklist

• Compress and size images correctly; serve modern formats where supported.
• Reserve space for images and embeds so layout does not shift.
• Reduce and defer render-blocking scripts.
• Move heavy JavaScript off the critical path.
• Use a capable hosting provider and a CDN.
• Remove plugins or scripts that load on every page but are only used on a few.
• Preload your hero image and fonts that matter for the first paint.
• Audit third-party scripts — each one adds work for the browser.

Common mistakes to avoid

Two mistakes are common. The first is optimising only the lab score in PageSpeed Insights while ignoring what real visitors experience — lab tests on a fast office connection do not reflect a phone on mobile data. The second is treating Core Web Vitals as the only performance goal. They are important, but a page that passes all three can still feel slow if the content itself is not what the visitor wanted. Speed is part of the experience, not the whole of it.

Where this fits

Core Web Vitals are one part of a healthy site, alongside good content and sensible structure. If your scores are weak, our website speed optimisation work covers exactly this: measuring, diagnosing and fixing the specific causes on your site. It also feeds into the SEO fundamentals that help rankings, and the same speed work reduces cart abandonment if you run a store.

Start by measuring, fix the biggest problem first, then measure again. The numbers will tell you whether the work is working — and that is a better guide than any checklist alone.