Optimize Core Web Vitals
Improve LCP, INP, and CLS with measurable budgets, prioritized images and scripts, and a release workflow that catches regressions early.
Posted by
Marc LouRelated reading
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Measure before optimizing
Core Web Vitals describe how a page feels: whether the main content arrives quickly, whether interactions respond promptly, and whether the layout stays stable. Establish mobile and desktop budgets before changing code.
1. Protect the largest image
Your LCP element should not compete with hidden animations, large fonts, or blocking scripts. Preload the hero asset when needed, serve responsive sizes, and make the fallback background occupy the same space as the final image.
2. Break long interaction work
Input delay often comes from one large task. Split heavy loops, avoid synchronous work after click, memoize expensive derived values, and keep hydration boundaries small so the browser can respond while the page settles.
3. Reserve every dynamic box
Give ads, badges, embedded media, and async lists explicit height or aspect ratios. A layout that never shifts is faster to use, even when the network is slow.
4. Add a release gate
Run Lab checks on key templates and collect field data after release. A page that passes on a fast laptop can still fail on a mid-range phone, so test the devices your customers use.