Web development and performance
What is WebP?
WebP is an image format offering roughly 25 to 35 percent smaller files than JPEG at comparable quality, with support for transparency and animation. It is supported by every current browser and is the sensible default fallback beneath AVIF.
Also called: WebP image format
Where it sits now
AVIF compresses better again — typically 30 to 50 percent smaller than WebP — but encodes more slowly and has slightly narrower tooling support. The practical answer is to serve AVIF first, WebP second, and the original format last, using a picture element.
Getting the sizing right matters more than the format
Serving a 2000-pixel-wide image to a 390-pixel phone wastes far more than any format choice saves. Generate several widths and let srcset and sizes pick — that single change usually outperforms the entire format debate.
What not to convert
- Logos, icons and line art, which belong in SVG
- Images that need to be downloaded and edited by the client
- Anything already small enough that the conversion saves a few kilobytes
Where this is covered in depth
A definition can only go so far. Image SEO: findable images that do not wreck your page speed covers this properly — 3 minutes, free, no email required.
Who wrote this
Anas Bin Masud builds e-commerce sites and does technical SEO for businesses in the UK, Canada and Pakistan. These definitions come from client work rather than from a content brief — where an entry describes a mistake, it is usually one found on a real site. More about how I work.