JPEG XL: The Storage Solution Apple (and Your Drive) Has Been Waiting For
With Apple’s adoption of JPEG XL in their OS’s, a significant opportunity for storage optimization has emerged. JPEG XL is designed to replace both JPEG and PNG with superior compression while maintaining or even improving visual quality. Yet despite this major step forward, Apple’s development tools haven’t fully caught up – while you can add JXL files to an app, Xcode does not yet offer full support (looking at you, Asset Catalog).
Thinking about the massive amounts of space you’d save converting an entire Photos library to JXL got me wondering about other areas that could benefit. Looking at the storage consumed by apps on the iPhone, iPad, and Mac, it’s clear that the Application folder itself is a massive target for optimization (even if Apple would rather sell you those insanely expensive storage upgrades).
PNG to JXL Savings in the macOS iMovie App
I used iMovie on my Mac as an example (version 10.4.3 on macOS Sequoia 15.3.2). The app takes up 4.2 GB, packed with supporting images and videos. Using a script from the previous article on JXL space savings in Photos, I calculated the total size of 2,353 PNG files within the app:
Total: 698.2 MB
Converting those losslessly to JXL, I get:
Total: 374.2 MB
That’s 46.4% smaller, nearly cutting the size in half. Now, what happens if we scale that across all PNGs in the Applications folder? Total PNG size across the entire Applications folder was:
Total: 1.62 GB
We’re looking at an easy storage win of ~750 MB. If developers embraced lossy JXL with transparency instead of lossless PNG, the savings would be even greater – and likely unnoticeable to users in terms of quality.
JPEG to JXL Savings
Next, I examined the JPEG files in iMovie, which collectively take up:
Total: 353.4 MB
Using JXL’s lossless JPEG transcoding, the result was:
Total: 279 MB
That’s 21.1% smaller, slightly better than the expected 20% average for lossless JPEG transcoding. But the real gains come when images are originally saved as JXL rather than first being encoded as JPEG. With native JXL, we could expect 40-50% savings AND better visual quality.
Scaling that across the entire Application folder’s JPEGs, we see a total size of:
Total: 1.07 GB
Applying the minimum 20% savings would reclaim hundreds of megabytes, while JXL-native images could reduce it by half a gigabyte or more. And while this is great on the desktop, it's even more exciting for the impact on the iPhone, where space is even more constrained.
JPEG XL’s System-Wide Impact
The numbers speak for themselves: implementing JPEG XL across Apple’s ecosystem could free up gigabytes of storage across billions of devices. Just imagine the bandwidth savings if every App Store update download leveraged JXL!
While Apple has taken a crucial first step by enabling JXL in its OS releases, the true potential of this technology will only be realized when developers integrate it into their workflows. Xcode’s lack of full support for JXL is currently a hurdle, but hopefully Apple (more) fully embraces the cutting-edge image format.
For users with limited device storage – especially those with base model iPhones and MacBooks – this can’t happen soon enough. The technology is ready. The benefits are undeniable. Now it’s just about making it the standard!
*JXL test compression done using libjxl version 0.11.1 and effort 7.