The iPhone 16 family has arrived and includes many new features, some of which Apple has played very close to its vest. One such improvement is the inclusion of JPEG-XL file types, which promise improved image quality compared to standard JPEG files while delivering relatively smaller file sizes.
What Is JPEG-XL?
JPEG-XL is a next-generation image encoding standard formally standardized in early 2022. Since then, JPEG-XL (.jxl) has been adopted by numerous operating systems and applications, albeit with some notable holdouts.
Apple and its various software iterations have supported JPEG-XL for at least a year, including in Finder, Preview, Final Cut Pro, Pages, Photos, Mail, Safari, and more. Adobe has also supported the format for a while, including in Adobe Camera Raw and Lightroom Classic.
Despite JPEG-XL supporting reversible JPEG transcoding and being superior to JPEG in terms of quality and efficiency, the format has yet to be widely adopted. Neither Chrome nor Firefox, two very popular web browsers, support the format natively, for example. Extensions are available to support JPEG-XL files, but they’re not installed by default.
The creators of the JPEG-XL standard cite the format’s ability to reduce file size while delivering “unmatched quality-per-byte.” Compared to a standard JPEG, a JPEG-XL file is up to 55% smaller while providing a cleaner image that is visually lossless. Gone are typical JPEG artifacts.
Although it’s easy to appreciate the technical advantages of JPEG-XL, it is also worth pointing out a substantial benefit of smaller file sizes: reduced environmental impact. As the world generates increasing amounts of data, it’s essential to consider ways to reduce data load. All that stuff lives somewhere, and wherever it is, it requires energy to operate.
It’s also important to note that JPEG-XL supports wide-gamut and high dynamic range images. “JPEG-XL is specifically designed to handle the rich colors of high-precision, high-dynamic range images,” the creators explain.
The format supports up to 32 bits per channel, supports RGB and CMYK delivery, works with multiple frames, and is open source.
.jxl files support RGB, YCgCo, and XYB color space. The RGB color space is familiar to most photographers, but XYB? That’s an odd one. This color space is built on the physiological processes by which people see.
“XYB facilitates perceptually uniform quantization,” the JPEG-XL standards body explains. “JPEG-XL uses a color space derived from LMS called XYB. Based on the lower spatial density of S cones, this is interpreted as a hybrid color theory where L and M oppose each other while S is handled trichromatically. As a result, less data is needed for storing blue signals without losing much quality. JPEG-XL’s colorspace was derived from Guetzli’s butteraugli metric and is based on Google’s Pik project.”
Overall, JPEG-XL addresses many of JPEG’s shortcomings. The 30-year-old format is not very efficient, only offers eight-bit color depth, doesn’t support HDR, doesn’t do alpha transparency, doesn’t support animations, doesn’t support multiple layers, includes compression artifacts, and exhibits banding and visual noise. JPEG-XL tackles these issues, and unlike WebP and AVIF formats, which each have some noteworthy benefits too, JPEG-XL has been built from the ground up with still images in mind.
Why JPEG-XL? Why Now?
As for why it is including JPEG-XL in the iPhone 16 Pro, Apple tells PetaPixel that the format promises two primary benefits over standard JPEG format: improved image quality and better compression performance. If there’s a 32MB JPEG image, that same photo will be 24MB in lossless JPEG-XL and, even more impressively, about five megabytes in perceptually lossless format.
Apple has wrapped JPEG-XL photos inside a DNG container, enabling ProRAW files to retain their flexibility while being significantly smaller — up to nearly five times smaller.
So, what’s the catch? Apple admits that JPEG-XL is not universally adopted or supported, at least not yet, so it is not the ideal choice for every person. Each user will need to evaluate their workflow and needs and determine if JPEG-XL fits. JPEG-XL’s benefits won’t mean much to someone who works with software or platforms that don’t support the file.
As Apple explains on the new iPhone models, JPEG-XL files are supported on iOS 17 and later and macOS 14 and later. However, as mentioned, these .jxl files are wrapped in a DNG container, so you can’t just fire off .jxl files from the iPhone 16 Pro.
As has been the case with some of Apple’s other early adoptions, like Thunderbolt, not everything always works in every case. One can just look at the rollout of the HEIC format in the photo space for evidence of how new formats don’t always take hold and receive fast, widespread support. Compared to JPEG-XL, HEIC — an implementation of HEIF — is just not good.
With JPEG-XL, while the benefits of the format are obvious and numerous, there are apt to be growing pains. Apple has done its part to limit these issues by offering JPEG-XL support across its platforms and utilizing DNG containers.
The other side of the coin is that because Apple is adopting and supporting JPEG-XL, other companies may follow suit. While Samsung added JPEG-XL to its latest Galaxy smartphones earlier this year, that doesn’t carry the same weight as Apple bringing JPEG-XL to its latest smartphones and supporting it across its entire ecosystem.
That’s not to say that JPEG-XL is a few short months away from being as ubiquitous as the standard JPEG image format. It will take time, and there’s no guarantee the format will ever be universally supported.
JPEG-XL addresses many of the problems of JPEG images, so hopefully, JPEG-XL will receive widespread support. As Apple fully understands, JPEG-XL is clearly the superior format for photographers.
A Welcome Improvement With Some Practical Concerns
For now, those who happily live inside Apple’s walled garden will benefit from JPEG-XL. Even when wandering outside the Mac/iPhone/iPad ecosystem, using JPEG-XL can be a painless experience. It’s easy enough to open and edit JPEG-XL files in Adobe software, for example.
However, beyond that, support will come later or may not come at all. JPEG is old and outdated, but its age has come myriad support and compatibility. Fortunately, reverse transcoding between JPEG and JPEG-XL is possible, but even that still requires development efforts. The point is that just because JPEG-XL is obviously better than many competing formats, it doesn’t mean everyone will adopt it.
For iPhone photographers, the benefits far outweigh the potential downsides. There’s little doubt that JPEG-XL is an excellent image format that offers the quality of heavyweight formats with a file size even smaller than that of JPEGs. What would typically be a 75-ish megabyte ProRAW Max file will be about 20MB in a lossy ProRAW format using JPEG-XL compression. A lossless file is still under 50MB. Without compromising quality, those are significant storage savings.
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