Mozilla Does Not Agree with Google, to Stick with and Improve JPEG

By Mozilla [Public domain], via Wikimedia Commons

By Mozilla [Public domain], via Wikimedia Commons

As Google promotes a new image format aimed at making image files smaller and web page loading times faster, Mozilla takes a stand and implies that a new format is unnecessary. Mozilla takes a path different from Google’s to pursue the development of a better JPEG. The maker of the popular Mozilla Firefox web browser thinks that there is no need for a new image format, that what is needed is to simply improve JPEGs.


The improvement Mozilla wants to introduce to JPEG comes in the form of MOZJPEG 2.0. This is a new JPEG compression library designed to reduce file sizes by approximately 5% compared to the popular LIBJPEG-TURBO. MOZJPEG 2.0 employs trellis quantization to improve the compression of both baseline and progressive JPEGs without compatibility issues.

This new compression library offers a number of improvements. It comes with a CJPEG utility that supports JPEG input to simplify re-compression workflows. It offers new options to specifically tune for PSNR, PSNR-HVS-M, SSIM, and MS-SSIM metrics. Additionally, MOZJPEG 2.0 generates a single DC scan by default to address incompatibility issues with decoders that are unable to handle arbitrary DC scans.

Why Mozilla is Sticking with JPEG

Mozilla decided to keep the JPEG format and simply focus on enhancing it instead of adopting a new format mainly because of two reasons. The first reason is the result of Mozilla’s own study where they learned that WebP does not provide consistent advantage compared to JPEG. The second reason is to ensure compatibility. The reaction on Facebook’s use of WebP is a concrete example of how compatibility can be a problem in shifting to a new format. Until now, not many applications have support for WebP. Facebook already asked Firefox back in 2013 to add support for WebP but Firefox continues to decline.

Firefox has a good reason to stick with JPEG since the JPEG specification only describes the behavior of the image decoder or the process that reconstructs an image out of compressed data. JPEG does not provide specifications on the encoding of an image, it is something left open. Another software or application will be responsible for creating a compressed image that can be decoded properly. This might sound unusual but it is the common practice in lossy compression formats. It makes sense because it enables advances in the future without the need to create an entirely new specification.

By Sean Martell for Mozilla [2] [3] [see page for license], via Wikimedia Commons

By Sean Martell for Mozilla [2] [3] [see page for license], via Wikimedia Commons

Mozilla’s goal is to develop a production-quality JPEG decoder with enhanced compression without sacrificing compatibility with the encoders already available in most programs and devices. Mozilla is also cognizant of the fact that there is a need to reduce image file sizes to reduce web page loading times. That’s why investigations are being done to explore the limits of JPEG and improve it.

Some say that Mozilla is just playing the politics of the Internet. The creators of Firefox might still be mad at Google for bringing Chrome into the web browser competition. After all, Firefox has been dethroned as the second most popular web browser despite its support for Google during those years when the Internet giant was competing with the likes of Yahoo and Microsoft’s search engine.

Image Quality Comparison

Google promotes WebP as the superior image format. However, it has to be noted that all loss compression formats, WebP included, incur data loss that leads to image quality degradation. The comparison on which one is better depends on the kind of test done. Testing image quality using machines or software may tend to consider WebP as the better format but the human eye may not really share the same judgment. Both software-based and subjective methods are required to determine the format with the better image quality in relation to the compression ability. Mozilla may think that sacrificing backwards compatibility may not be that warranted by the marginal advantages brought about by WebP.

By Christophe Mehay (Own work) [GFDL ( or CC-BY-SA-3.0-2.5-2.0-1.0 (], via Wikimedia Commons

By Christophe Mehay (Own work) [GFDL ( or CC-BY-SA-3.0-2.5-2.0-1.0 (], via Wikimedia Commons

The shift to a new format is a controversial topic but it appears Google is gaining momentum in getting things done as Facebook decided to run trials in serving WebP images. Many users have complained about the move but a Facebook backing is certainly a significant support for WebP. Mozilla, fortunately, also has the backing of Facebook as the social media giant also decided to test the upgraded JPEG format. Facebook even offered a $60,000 donation for the development. As to which one will prevail, only time will be able to tell. The good thing is that this competition is great for the image format especially used online. This means that advocates of the two major formats will try to outdo each other in delivering advantages – something that can only be considered good for users in the long run.