WebP
A Google-developed image format supporting lossy and lossless compression plus transparency and animation, typically 25-35% smaller than…
TechnicalAV1 Image File Format
AVIF
A modern image format based on the AV1 codec that generally compresses better than WebP, with wide but slightly less universal browser support.
In full
AVIF supports HDR, wide colour gamut and alpha transparency, and frequently halves WebP file sizes at equivalent perceived quality, at the cost of slower encoding. It is deployed with a `<picture>` element listing AVIF first, WebP second and JPEG last, or via CDN negotiation. For LCP-critical hero images the byte savings often translate directly into passing the 2.5 s threshold on mobile networks.
Example
`<picture><source type="image/avif" srcset="hero.avif"><source type="image/webp" srcset="hero.webp"><img src="hero.jpg" alt="…"></picture>`
Related terms
Largest Contentful Paint
A Core Web Vital measuring the render time of the largest image, video poster or text block visible in the viewport; good is 2.5 s or less…
srcset and sizes
HTML attributes that offer the browser multiple image candidates at different widths so it can pick the smallest file that fits the layout…
Content Delivery Network
A distributed network of edge servers that caches and serves content close to users, reducing latency and offloading the origin.
Core Web Vitals
Google's set of three field-measured user experience metrics — LCP, INP and CLS — used as part of the page experience signals in ranking.