WebP is a method of lossy compression that can be used on photographic images. The degree of compression is adjustable so a user can choose the trade-off between file size and image quality.
A WebP file consists of VP8 image data, and a container based on RIFF. Webmasters, web developers and browser developers can use the WebP format to create smaller, better looking images that can help make the web faster.
Some huge reductions in file sizes without an loss of quality. So far I’m impressed with the new Google WebP image format.
How WebP works:
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.
Sample of side-by-side comparison: