Image glossary
WebP
Also known as WebP format, .webp
WebP is an image format developed by Google that supports both lossy and lossless compression with transparency, and produces files roughly 25-35% smaller than JPEG at matched visual quality.
What it is
WebP is a raster image format introduced by Google in 2010 and supported by every current browser since 2020. Its distinguishing feature is that it is really two codecs in one container: a lossy mode derived from the VP8 video codec, and a lossless mode with its own entropy coding. Both support an alpha channel, which JPEG does not.
That dual nature is what makes WebP useful as a single default. A photograph becomes lossy WebP and lands around a quarter to a third smaller than the equivalent JPEG. A screenshot or a logo becomes lossless WebP and lands around 20-30% smaller than the equivalent PNG, with transparency intact. One format covers both jobs, so you stop maintaining a rule about which files are PNG and which are JPEG.
Where it wins
On the web, almost everywhere. Browser support stopped being an argument years ago, and the size advantage applies on every page view rather than once. WebP also encodes fast — fast enough to run over a folder of hundreds of images without the wait becoming the reason you skip the step.
Lossy WebP with an alpha channel is a specific and underused win: a cut-out photograph saved this way is dramatically smaller than the lossless PNG most people reach for, and in practice indistinguishable.
Where it does not
Outside the browser. Some desktop applications, email clients, print workflows and upload forms still refuse WebP, and when a link scraper cannot decode it there is no fallback — the preview simply comes back empty. This is why an Open Graph image should be PNG or JPEG even though WebP would be smaller.
It is also not the best compressor available. AVIF beats it by another 15-25% at matched quality, particularly on gradients and flat colour. WebP's advantage over AVIF is encode speed, which matters when you are processing many images rather than one.
A common disappointment is worth naming: converting an already-compressed JPEG to WebP often saves much less than the headline figures, sometimes nothing. The JPEG already discarded what both formats would discard, so you are compressing the remainder. The quoted savings are measured from an uncompressed original.
Choosing a mode
The format name does not tell you which mode a file used, which is why "save it as WebP" is not a complete instruction. Photographs want the lossy mode at quality 75-85. Anything with text, hard edges or flat colour — screenshots, diagrams, logos, UI assets — wants the lossless mode, where the compression is exact and the edges stay crisp.
Tools that work with this
Related terms
- AVIFAVIF is an image format derived from the AV1 video codec that compresses roughly 40-55% smaller than JPEG at matched visual quality, at the cost of much slower encoding.
- JPEGJPEG is a lossy raster image format from 1992 that remains the most universally readable image format in existence, with no support for transparency.
- PNGPNG is a lossless raster image format with full alpha transparency, excellent on screenshots and line art and very inefficient on photographs.
- Lossy compressionLossy compression permanently discards image information judged imperceptible in order to make files dramatically smaller, and the discarded data cannot be recovered.
- Lossless compressionLossless compression makes a file smaller by encoding redundancy more efficiently, and decompression returns data bit-for-bit identical to the input.
- Alpha channelAn alpha channel is a per-pixel transparency map stored alongside the colour channels, recording how much of each pixel is opaque.
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