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Facebook joins Mozilla to slim down Web's images

Mozilla and Facebook are joining forces in an unusual alliance to save bandwidth by reducing the size of image files on the Web.

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Mozilla studied Google's WebP image format and wasn't convinced it's significantly better than decades-old JPEG. In this chart, a lower number means a smaller file size for a given quality level compared to JPEG. Mozilla used several tests on several images, and this is just one of its graphs. Mozilla

Long live the lowly JPEG.

At least for today, that's the cheer coming from the offices of Facebook and Mozilla, thanks to a new partnership which aims to cut down JPEG size without resorting to the time-consuming introduction of a new image format.

The social network and the browser maker announced on Tuesday that they are working on improving the state of JPEG encoders, the tools used to shrink image size while retaining a quality appropriate for Web viewing, as Facebook adopts the second version of Mozilla's home-brewed JPEG encoder mozjpeg.

Mozjpeg was first introduced earlier this year as a JPEG encoder that reduces image size on average by 5 percent, and in many cases by as much as 10 to 15 percent. For sites like Facebook that process millions of images daily, that quickly adds up to major bandwidth savings.

"With the right improvements to JPEG, the format is pretty competitive," against newer image compression formats, Mozilla chief technology officer Andreas Gal told CNET. Because such a huge fraction of images on the Web are JPEG, Gal said, mozjpeg could succeed "without having to fight the long adoption curve."

Mozilla has long resisted the calls of Google and others to adopt Google's new WebP image format. A Mozilla study from 2013 argued that JPEG quality depended on which metric it was being judged by, and therefore newer formats such as WebP or JPEG XR were not significantly better than the decades-old JPEG.

The JPEG has come under fire in recent years as tech companies have searched for an alternative that maintains or improves image quality while reducing the size of the image. Google had gotten Facebook to support it, and Facebook even had pressured Mozilla to try it out.

In a prepared statement, Facebook sounded enthusiastic for the encoder improvement, and even donated $60,000 to mozjpeg development.

"Facebook supports the work Mozilla has done in building a JPEG encoder that can create smaller JPEGs without compromising the visual quality of photos," Facebook software engineer Stacy Kerkelasaid. "We look forward to seeing the potential benefits mozjpeg 2.0 might bring in optimizing images."

Since the JPEG encoder is implemented by the site owners, and not the browser vendor, Mozilla sidesteps much of the political conflict that has been a hallmark of Web standards development.

Mozilla wouldn't reveal which other image-heavy sites it was discussing mozjpeg 2.0 with, although Gal did note that mozjpeg would have to be adopted for JPEG on the Web use by only a few sites for it to be considered a success.

"Image traffic on the web is asymmetrical. You can solve 80 percent of the problems with just a few sites," he said, adding that he expected the technology to be adopted quickly.

It has also donated $60,000 to contribute to the ongoing development of the technology, including the next iteration, mozjpeg 3.0.