What Are Core Web Vitals? A Beginner's Guide to Website Speed
July 30, 2026
The three metrics that matter most
Largest Contentful Paint (LCP) measures how long the biggest visible element takes to load — a slow LCP feels like a page that's stuck loading. Cumulative Layout Shift (CLS) measures how much content unexpectedly jumps around as a page loads — a high CLS is that annoying moment where you tap a button just as an ad loads in and you tap something else by mistake. Total Blocking Time (TBT) reflects how responsive a page feels to actual clicks and taps while it's still loading.
Why these matter for SEO, not just user experience
Google uses Core Web Vitals as a ranking signal, especially for mobile search — two pages with similar content can rank differently partly based on how these metrics compare, since Google prioritizes results that load fast and feel stable to real visitors.
How to check your own site's score
Use the free Website Speed Checker — enter your URL and you'll get separate Mobile and Desktop scores, since mobile performance is usually the more important one for search ranking, plus a list of specific issues (unused CSS, unoptimized images, render-blocking resources, and more) worth fixing first.
Fixing the basics before chasing a perfect score
Common quick wins include compressing large images (try the free Image Compressor before uploading new photos to your site), removing unused CSS/JS, and reserving space for images and ads so content doesn't jump around as it loads. A perfect 100 score isn't usually the goal — fixing the worst-scoring metric first tends to matter more in practice.