Google promises to speed up the web with new image format

Posted by Emma Woollacott

Google has started pushing an alternative to the JPEG image format in a move which it says could speed up the web.

Most of the formats in general use are over a decade old, and the company says that they're consistently responsible for most of the latency users experience. Images make up about 65 percent of the bytes transmitted per web page, with lossy formats such as JPEG the worst offenders.

WebP, says Google, improves matters considerably by using an image compressor based on the VP8 codec that Google open-sourced in May 2010.

"While the benefits of a VP8 based image format were clear in theory, we needed to test them in the real world," says product manager Richard Rabbat.

"In order to gauge the effectiveness of our efforts, we randomly picked about 1,000,000 images from the web (mostly JPEGs and some PNGs and GIFs) and re-encoded them to WebP without perceptibly compromising visual quality. This resulted in an average 39 percent  reduction in file size."

Rabbat says he expects developers to achieve even better file size reduction in practice, when starting from an uncompressed image.

Google is releasing a conversion tool to the new format, and says it hopes to work with broswer and web developers to improve the WebP spec and add native support.

WebP images can't be viewed until browsers support the format, but Microsoft says it's developing a patch for WebKit to provide native support for WebP in an upcoming release of Google Chrome. It also plans to add support for a transparency layer, or alpha channel, in a future update.

Google's released a series of images for comparison, here. But many observers are already suggesting that WebP offers little improvement over existing formats.

"With several other formats already available which offer similar advantages, what we need is better browser support, not another format to deal with," reads one comment on the Chromium blog.

"With two competing successors to JPEG and no real fallback options, developers will basically be forced to use neither and stick with JPEG."