Core Web Vitals: what to fix first

Core Web Vitals measure three things real visitors feel: how fast the main content appears, how quickly the page responds to input, and whether things jump around while it loads. Google assesses them from real-user data at the 75th percentile, so a fast laptop on office Wi-Fi tells you very little.

The three metrics and their targets

• Largest Contentful Paint (LCP): main content visible within 2.5 seconds.
• Interaction to Next Paint (INP): responses to taps and clicks within 200 milliseconds.
• Cumulative Layout Shift (CLS): a score below 0.1.

LCP: make the hero arrive first

Find the LCP element (usually a hero image or headline) and make sure nothing delays it. Serve the image in a modern format at the right size, don’t lazy-load it, consider preloading it, and cut render-blocking CSS and third-party scripts that load before it. Slow server response is often the hidden cause, so check time to first byte too.

INP: give the main thread room

Poor INP almost always means long JavaScript tasks. Audit tag managers and chat widgets first, defer what isn’t needed for the first interaction, and break up heavy event handlers so the browser can paint between them.

CLS: reserve space

Set width and height on images and video, reserve space for ads and embeds, and avoid injecting banners above existing content. Web fonts can shift text as they load; matched fallback fonts keep that movement small.

Measure, fix, re-measure

Use the Search Console Core Web Vitals report to find failing templates, lab tools to diagnose them, and real-user data to confirm the fix. Field data updates over a rolling 28-day window, so give changes time to show.