A Practical Core Web Vitals Checklist

Core Web Vitals are not just metrics. They are signals Google uses to rank your site. If your pages are slow or janky, you lose visibility in search results. The good news is that most issues have straightforward fixes.

Start with Largest Contentful Paint (LCP). This measures how long it takes for the main content to load. You want this under 2.5 seconds. The biggest culprits are usually unoptimized images and slow server response times. Use modern image formats like WebP, add width and height attributes to prevent layout shifts, and lazy load images below the fold.

Next is Cumulative Layout Shift (CLS). This tracks how much your page jumps around while loading. Reserve space for images and ads before they load. Set explicit dimensions on media elements. Avoid inserting content above existing content unless it is in response to a user action. A score under 0.1 is good.

First Input Delay (FID) measures how quickly your site responds to user interactions. Heavy JavaScript execution blocks the main thread and makes buttons feel sluggish. Break up long tasks, defer non-critical scripts, and use code splitting to reduce the amount of JavaScript that needs to parse on initial load.

The newer metric, Interaction to Next Paint (INP), is replacing FID. It measures responsiveness throughout the entire page lifecycle, not just the first interaction. Keep your JavaScript lean, avoid blocking the main thread, and test on mid-range devices, not just your high-end development machine.

Measure with real user data, not just lab tests. Lighthouse gives you a baseline, but field data from actual visitors tells you what performance looks like in the real world. Use Google Search Console to see your Core Web Vitals scores for real traffic.

Fix the worst offenders first. One massive image or render-blocking script can tank your scores. Start there, measure again, then move to smaller optimizations. Small improvements add up, but the big wins come from fixing the obvious problems first.