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Web & Accessibility

Core Web Vitals: the three numbers that move conversion

1 min read

A performance dashboard and speed gauge measuring how fast a web page loads

Performance work spirals easily — you can generate a hundred findings and fix none that matter. Core Web Vitals gives you three numbers that both search engines weight and users actually feel. Start there.

The three that matter

  • LCP (Largest Contentful Paint) — how fast the main content shows. Usually your hero image or headline.
  • INP (Interaction to Next Paint) — how quickly the page responds when someone taps or clicks.
  • CLS (Cumulative Layout Shift) — how much the page jumps around while loading.

Tip

Measure with field data, not just your laptop. Your dev machine on fast wifi hides the exact problems your users on mid-range phones are living with. Real-user metrics are the truth.

The usual culprits

LCP is often an unoptimized hero image or a slow server response. INP is usually too much JavaScript running on the main thread. CLS is images and embeds without reserved space.

Reserve space to kill layout shift
// Give media explicit dimensions so nothing jumps as it loads
<Image src="/hero.jpg" alt="…" width={1600} height={900} priority />

Watch out

Chasing a perfect lab score while ignition-slow third-party scripts tank the real experience is a trap. Fix what field data shows real users hit, in order of impact.

We build performance-aware, accessible web experiences — fast where it counts, measured with real data, and maintainable so the numbers stay good after launch, not just on day one.

Related tipAccessibility isn't a checklist — it's a design decision

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