WebP is a comparatively new image format employing both lossy and lossless compression. It is currently developed by Google, based on technology acquired with the purchase of On2 Technologies. As a derivative of the VP8 video format, it is a sister project to the WebM multimedia container format. WebP-related software is released under a BSD license.

The format was first announced in 2010 as a new open standard for lossily compressed true-color graphics on the web, producing smaller files of comparable image quality to the older JPEG scheme. On October 3, 2011 Google announced WebP support for animation, ICC profile, XMP metadata and tiling (compositing very large images from maximum 16384×16384 tiles).

On November 18, 2011 Google began to experiment with lossless compression and support for transparency (alpha channel) in both lossless and lossy modes; support has been enabled by default in libwebp 0.2.0 (August 16, 2012). According to Google’s measurements, a conversion from PNG to WebP results in a 45% reduction in file size when starting with PNGs found on the web, and a 28% reduction compared to PNGs that are recompressed with pngcrush and pngout.

Google has proposed using WebP for animated images as an alternative to the popular GIF format, citing the advantages of 24-bit color with transparency, combining frames with lossy and lossless compression in the same animation, and as well as support for seeking to specific frames. Google reports a 64% reduction in file size for images converted from animated GIFs to lossy WebP, and a 19% reduction when converted to lossless WebP.