Learn · Performance & optimization
CLS measures visual stability: how much the page unexpectedly jumps around as it loads. The target is under 0.1. You've felt bad CLS when you go to tap a button and an image or ad loads above it, pushing everything down so you tap the wrong thing.
The usual causes are images and embeds without reserved space, ads that push content, and fonts that swap and reflow text. Fixing it means setting explicit dimensions for images and video, reserving space for anything that loads late, and handling fonts carefully.
CLS is often the easiest vital to fix because the causes are concrete and the solutions are mechanical. A stable layout also just feels more trustworthy and polished, quite apart from the ranking benefit.
Updated July 2026
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Core Web Vitals are Google's three metrics for real-world page experience: LCP (loading speed), INP (responsiveness), and CLS (visual stability). As of July 2026 the "good" targets are LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1, measured on real visitors at the 75th percentile.
Compress images, use modern formats like WebP or AVIF, size them to how they'll actually be displayed, and load offscreen ones lazily. Images are usually the heaviest part of a page, so optimizing them is the single biggest speed win on most sites.
LCP measures how long it takes for the largest visible element (usually the main image or heading) to load and appear. It's the closest single number to "how fast does this page feel to load." The target is under 2.5 seconds for the good rating, measured on real visitors.
INP measures responsiveness: how quickly the page reacts visually after you tap, click, or type. It replaced the older FID metric in March 2024 and looks at interactions across the whole visit, not just the first. The target is under 200 milliseconds. It's the most commonly failed vital in 2026.
Speed affects money directly. Faster sites keep more visitors, convert more of them into customers, and rank better in search. Study after study shows that as load time rises, people leave and sales drop. A slow site quietly loses revenue before anyone reads a word of your content.
A CDN (content delivery network) is a network of servers around the world that store copies of your site's files and serve them from the location nearest each visitor. That shorter distance means faster loading. Most sites with a global or growing audience benefit, and many hosts now include one.