What is JPEG XL?

The JPEG format has been one of the best-known file formats for images and photos for several decades. The format used since 1992 is usually used with the extensions .jpeg or .jpg. It is known for its various compression rates, which are reflected in decreasing image quality as the file size decreases. Over the years there have always been adjustments and different sub-formats of JPEG for different (specialist) areas. But in recent years, JPEG XL has been developed, which should finally replace the previous format. But what is JPEG XL? What advantages does it bring over the old image and photo format? And what does the name mean?

What does "JPEG XL" stand for?

Because of the "XL" appendix, one could now assume that the new file format is intended for particularly large images - for example for poster designs, panorama photographs, RAW photos or the like. But that would be short-sighted, especially since the name does not even refer to the resolution, pixel density or memory size of the files equipped with it. The name JPEG XL consists of the following components:

• JPEG stands for the Joint Photographic Experts Group
• X stands for the JPEG formats since 2000, among which are XT, XR and XS
• L stands for Long-Term to indicate that the current file format is to be superseded

Properties of JPEG XL as an image file format

The new image and photo file format JPEG XL with the file extension .jxl is intended to address current and future expectations that are placed on corresponding files. Because in addition to reducing the file size with a fairly well-preserved image quality, there are now many other application goals. For example, JPEG XL should be adapted to the requirements of responsive web environments, i.e. the choice of size and resolution with regard to the target device should be better and faster.

Encoding and decoding should run quickly and efficiently without additional hardware, even on mobile devices. There is also downward compatibility, so that servers, for example, only have to store a JPEG XL file in order to be able to offer both this and the reduced JPEG file. Existing JPEG files can be converted and converted back without loss, which should simplify the switch to the new format.

But that's not all. In addition to using it on the web and on servers, there are other tasks for image files that JPEG XL should be able to do. For professional photography, for example, there is an extended color spectrum, HDR support, greater bit depth and 360° images. It also supports animations (like animated GIF files), preserves alpha channels, includes layers and thumbnails, and offers lossless and progressive encoding.

Brief outline of the development of the file format

The new JPEG XL file format was first discussed in 2018 by the Joint Photographic Experts Group. At that time there weren't any of the specifications or standards that are fixed today; these were initially demanded by the members of the group. This is how the development of the desired JPEG successor began. Then, from seven proposals, two were selected and merged (FUIF by Cloudinary and PIK by Google). The standardization of .jxl started in 2021 and continued in 2022. Version 2022 was released in September 0.7; version 0.8 followed in January 2023.

Current use and integration of JPEG XL

So there is currently no "full" version of the file format or the software and codecs behind it. Nevertheless, there are already some apps that can handle it. I used e.g. B. on Mac and PC the Affinity programs from Serif. And these can be in the version 2 (e.g. Affinity Photo 2) Output images and graphics as JPEG XL. Chalk supports the format from version 5.1. And even lesser known apps have already implemented the format - IrfanView, ImageMagick, MConverter, gThumb, Pale Moon and so on.

Other programs and systems do not require an update of the official software version, but the integration of a (third-party) plugin. Under macOS this affects e.g. B. Quick Look. On Windows, for example, the photo display and the explorer can be expanded. For the graphics app GIMP there is also a plugin that is supposed to support JPEG XL from version GIMP 2.1. My disclaimer at this point: I haven't tried any of it, only looked for the export option in Affinity Photo 2.

For use on the web, of course, you would also need Web browser support the new format. Up to a point they already have. Chromium applications like Google Chrome and Microsoft Edge had implemented JPEG-XL support, but it was announced in October 2022 that the feature would be removed. And even with Mozilla's Firefox, there was no long-term support in official versions, but only in the nightly version, a preliminary version for testing new features.

More information and reading

I hope this short summary of the topic has helped you to get an idea (haha) of the new file format. If, in addition to the application examples such as 360° photos, professional photography, animated images and Co., you are also interested in the technical background and further development, then take a look at these pages, which I used as sources for this article:

• Official page on the subject at the Joint Photographic Experts Group: View here
• Goals and specifications of the new format as a PDF document: View here
• Wikipedia article with more information on format and history: View here

Johannes Domke

After graduating from high school, Johannes completed an apprenticeship as a business assistant specializing in foreign languages. But then he decided to research and write, which resulted in his independence. For several years he has been working for Sir Apfelot, among others. His articles include product introductions, news, manuals, video games, consoles, and more. He follows Apple keynotes live via stream.