WebP uses predictive coding to encode an image, the same methodology used by the VP8 video codec to compress keyframes in videos. Predictive coding uses the values in neighboring blocks of pixels to predict the values in a block, and then encodes only the difference (residual) between the actual values and the prediction.

The residuals typically contain many zero values, which can be compressed much more effectively. The residuals are then transformed, quantized and entropy-coded as usual. WebP also uses variable block sizes.

A WebP file consists of VP8 image data, and a container based on RIFF. The standalone libwebp library serves as a reference implementation for the WebP specification and is available at this git repository and as a tarball .

WebP is supported by a variety of tools. In addition, it is now natively supported in Google Chrome, the Google Chrome Frame plug-in for Internet Explorer, Opera 11.10 and Android Ice Cream Sandwich.

Developers have also added support to a variety of image editing tools. This release also provides a lightweight encoding and decoding library, libwebp and command line tools cwebp and dwebp for converting images to and from the WebP format. The full source code is available on the download page.

Convert your favorite collection from PNG and JPEG to WebP by downloading the precompiled cwebp conversion tool for Linux, Windows or Mac OS X.

Tell us your experience on the project's mailing list.