What is Cumulative Layout Shift (CLS)?
The Core Web Vital measuring visual stability: how much content jumps around while loading. Reserve space for images, ads, and embeds with width, height, or aspect-ratio boxes.
Related terms
Core Web Vitals
Google’s field-measured experience metrics: Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift. Roughly half of origins pass all three, so the work remains relevant.
Lazy Loading
Deferring below-the-fold images, video, and iframes until near the viewport. It trims initial page weight, the strongest lever on Core Web Vitals pass rates after server response.
Page Speed
How fast a page becomes usable, measured by field metrics like LCP and INP rather than single lab scores. Small gains compound commercially: a tenth of a second has moved retail conversions measurably.
Technical SEO
The crawling, indexing, rendering, and performance work that lets search engines reach, understand, and serve your pages. It covers directives, architecture, speed, and structured data rather than words on the page.
Crawling
How search-engine bots discover pages by following links, sitemaps, and directives. If a URL is never crawled, it cannot be indexed no matter how good its content is.
Crawl Budget
The number of pages a search engine will crawl on a site in a given period, driven by server capacity and demand signals. Large or slow sites must spend it on indexable, valuable URLs.