JXL (JPEG XL) is a new image file type you’ll see more of, and Chrome support is now working, too

I’ll be completely transparent, here: until I saw this flag in the list on my Chromebook, I didn’t even know JXL was even a thing. There are so many photo and video file types these days, it’s hard to keep up. At the end of the day, we all want high fidelity images that don’t take up gobs of space either on our phones, laptops, tablets, or servers. That’s a heavier lift than it sounds, and delivering such a digital image type that is agreeable to most as a standard makes this task that much more difficult.

The humble JPEG file format is 30 years old at this point – as old as the internet – and many of us feel the need for it to be replaced. JPEGs are great for file size, however, and they are universally adopted by basically every single electronic in the world. Seriously, go plug in a USB drive with some JPEG files on it, and I’d bet that your old television will be able to decode and display those pictures. With fancier, more-modern image formats, your mileage will surely vary.

A replacement has been tried before

Try as they might, there’s never been a success story when anyone has attempted to supplant the JPEG over the years. There have certainly been attempts with files types such as JPEG 2000 and JPEG XR, but we clearly don’t see those file types in regular use these days. When trying to replace something so many people use, you can’t simply swap one for the other: you have to create a path for success. Older attempts at modernizing the JPEG didn’t do this, but JPEG XL was started with this plan in place.

Using JPEG recompression, legacy JPEG files can be converted losslessly to the more compact JPEG XL format: existing JPEG files can be transferred seamlessly. These can be restored into the same JPEG file to maintain backward compatibility with existing JPEG applications.

Previous attempts to develop “next-generation” image formats, including JPEG 2000, JPEG XR, and now HEIC and AVIF, didn’t achieve this. A JPEG image must be decoded into pixels and then re-encoded with one of those other formats. This irreversible process results in generation losses.

In the JPEG XL Project, those challenges were considered from the start. The format was designed to overcome them as much as possible.

via JPEGXL.io

What is JPEGXL (or .jxl)?

Not simply a modern replacement for the aging JPEG, JPEG XL is a far more compact image file with far more capabilities than the standard JPEG. The full breadth of things that JPEG XL files are capable of is very long and frankly over my head, but I’ll drop a few of the things below that you can expect from JPEG XL as it becomes more and more of a standard file type.

• High fidelity to the source image (matches human perception)
• Supports alpha transparency
• High-speed encoding and decoding
• High compression ratio (20:1 to 50:1)
• Improved functionality and efficiency over traditional formats
• Progressive decoding (by resolution and precision)
• Lossless JPEG transcoding
• Support for both photographic and synthetic imagery
• Graceful quality degradation across an extensive range of bitrates
• Perceptually optimized reference encoder
• Support for wide gamut and HDR
• Support for animated content
• Efficient encoding and decoding without requiring specialized hardware

Not only will JPEG XL be faster with better image quality, the files will be smaller and simpler to work with, too. While I don’t understand some of the more-complex decoding/encoding stuff that goes on with images, I can fully appreciate a file format that maintains a better image quality than the standard JPEG while also keeping the file size smaller with a faster encode/decode to go with it.

One of the more important benefits will be the addition of alpha transparency. A huge hangup of the standard JPEG is the fact that you can’t remove backgrounds from images. So any time you need an image that uses any form of transparency, you are forced to what usually is a larger, less-compressed image format that isn’t great for use in bulk on the web. JPEG XL will eventually solve this problem.

Finally, I’m excited to see a compression rock star like JPEG XL have an animation option. How it will work and be supported will be the question, but assuming JPEG XL eventually gets universal adoption, we’ll be able to build animations like GIFs in a far more economical way, making smoother, better animations possible without demolishing data bandwidth.

Adoption is key

Clearly, the biggest hurdle for JPEG XL will be adoption. However, with backward compatibility with the existing JPEG spec and a royalty-free baseline, the folks behind JPEG XL (the JPEG committee, Google and Cloudinary) have crafted a truly worthy successor to the JPEG. But, even with all the best features in the world, a file type will always be held back if wide-ranging support isn’t on the table.

XL shares the same disadvantage as any new format that needs to be established: It lacks support. In addition, few operating systems support JPEG XL. There is a lack of browsers and image viewers that support it even though many browsers added support for JPEG XL behind a flag.

via JPEGXL.io

Right now, you can mess with JXL files in Chrome by turning on the flag found at chrome://flags/#enable-jxl, but the real benefits don’t show up with JXL until most operating systems and applications pick up support for the standard. As that happens, developers across the board will be able to leverage a more-efficient image format on everything from websites to applications by simply changing to JXL. Until then, we’ll keep an eye on this emerging file format and when the day comes, we’ll be looking to move our entire image library over to JPEG XL.