Web Performance Glossary

An advanced image format offering even better compression than WebP, based on the AV1 video codec.

A public dataset of real user experience data collected from Chrome browsers.

A geographically distributed network of servers that delivers web content from locations closer to users.

A set of three metrics (LCP, INP, CLS) that Google uses to measure user experience and as ranking factors.

A Core Web Vital that measures visual stability by quantifying unexpected layout shifts.

The system that translates human-readable domain names into IP addresses.

A performance metric measuring when the first content element is rendered on screen.

A deprecated Core Web Vital that measured the delay before the browser could respond to the first user interaction.

A major revision of HTTP that enables faster, more efficient web communication through multiplexing and other features.

A Core Web Vital that measures page responsiveness by tracking the latency of user interactions.

A Core Web Vital that measures how long it takes for the largest content element to become visible.

A technique that defers loading of non-critical resources until they're needed.

An open-source tool by Google for auditing web page quality including performance, accessibility, and SEO.

A browser hint that tells the browser to fetch a resource early because it will be needed soon.

Resources like CSS and JavaScript that prevent the browser from rendering content until they're downloaded and processed.

A metric measuring the time from request start until the first byte of the response is received.

A lab metric measuring the total time the main thread was blocked long enough to prevent input responsiveness.

A modern image format that provides superior compression for images on the web.