Why Firefox Doesn't Support Google's WebP Image Format

By Sam Cook

Google touts WebP as an alternative to JPEG, but Mozilla remains unconvinced.

The humble JPEG has been with us a long time, and has served the Internet’s adorable cat picture distribution needs quite well. But perhaps it’s time to rethink our go-to image file format, and build something even better from the ground up. That’s the philosophy behind Google’s WebP (pronounced “weppy”), which the company hopes will replace the old JPEG standby, and create a web full of pictures that look better, take up less space, and ultimately speed up our load times. Those sound like noble goals, for sure, but not everyone shares the company’s enthusiasm for WebP—aside from Chrome 12 and Opera, no browser supports the format, and Mozilla has outright refused to let it onto Firefox.

So what is WebP, and why is there so much disagreement surrounding it? Let’s take a look.

Like JPEG, WebP is a “lossy” form of compression that reduces file size by discarding some data. It’s rooted in the VP8 tech behind Google’s WebM video format, where the same methodology is used to create keyframes. WebP software uses predictive coding, where it guesses the content of a block of pixels based on the blocks around it. Then, the software only has to encode the differences between the actual block and the prediction. The end result, according to Google, is images that manage 39% more compression than JPEG with no difference in quality—they even have a gallery to prove it. And just like its video sister project, WebP is open source and released under a permissive free BSD license.

But Google’s evidence hasn’t convinced everyone, least of all Mozilla. The company’s Jeff Muizelar detailed his criticisms of WebP in a blog post, calling into question Google’s testing methods and pointing out that the format isn’t nearly as feature-rich as JPEG. To be fair, anyone who’s familiar with Google shouldn’t be surprised when one of their projects is rather half-baked. By nature, the company likes to iterate, putting fresh code out into the world so they can quickly improve it with new revisions. And based on Google’s recent WebP related moves, like adding support for it in Picasa and bringing in a list of new features, they aren’t nearly done with the format.

But as Muizerlar points out, even a much more refined WebP may not be enough to take over for JPEG. Image format adoption has traditionally been slow, and services rooted in using the older standard will need a considerable motivation to make the switch. One thing is for sure, though: to really have an impact, WebP needs support from more than two browsers. Perhaps once Google polishes it into a stronger JPEG competitor, they can make more headway winning over those developers.