Core Web Vitals in 2026: the fixes that work

We audit a lot of slow sites. The same four problems account for the overwhelming majority of failures, and none of them are the ones people arrive worrying about.

First: measure the right thing

Lighthouse in your browser is a lab test on your laptop over your office wifi. Google ranks on field data — real visitors on real devices, collected in the Chrome UX Report over 28 days.

Check field data in Search Console under Core Web Vitals, or in PageSpeed Insights (the top section, not the Lighthouse section below it). If lab and field disagree, field wins.

Fix 1: the LCP image

Largest Contentful Paint is usually a hero image, and it is usually failing for one of three reasons:

• It is lazy-loaded. The one image guaranteed to be in the viewport should never be lazy.
• It has no explicit priority, so the browser discovers it late.
• It is a 2MB JPEG being displayed at 800px wide.

In Next.js, that is priority on the hero <Image>, correct sizes, and letting the framework serve WebP or AVIF. This single fix moves more sites from red to green than everything else combined.

Fix 2: the fonts

Web fonts block text rendering, then reflow the page when they load. Two changes:

• font-display: swap so text paints immediately in a fallback.
• Preload the one font file used above the fold.

Then check your fallback stack. If your fallback is metrically nothing like your web font, swapping causes a visible jump that counts against Cumulative Layout Shift.

Fix 3: reserve space for everything that loads late

Every ad slot, embed, banner, and lazy image that appears without reserved space pushes content down and costs you CLS. The fix is unglamorous: explicit width/height or aspect-ratio on every element whose size you know in advance.

Cookie banners and notification bars deserve special attention — they are inserted late, at the top, on every single page.

Fix 4: stop shipping JavaScript nobody needs

Interaction to Next Paint punishes main-thread work. The usual offenders:

• A full charting or animation library imported for one component — the same discipline that keeps a dashboard fast.
• Analytics, chat, heatmap, and A/B tools all loading during page load.
• Client components that render static content and never needed to be interactive.

Run a bundle analysis, sort by size, and ask of each entry: does this need to load before the user interacts? Most third-party scripts can load after, and third-party scripts are usually the entire problem.

What we skip

Micro-optimisations that cost days and change nothing: shaving milliseconds off server response when your LCP image is 2MB, minifying already-gzipped assets, obsessing over a lab score while field data goes unmeasured.

Speed is only one way a site loses visitors — seven conversion mistakes covers the rest.

Fix the image, fix the fonts, reserve the space, cut the JavaScript. Re-measure after 28 days of field data — not the same afternoon.

Want a specific answer for your site? We run fixed-scope performance audits that come back with a prioritised list and the measured impact of each item.