Does Apple suggest that developers transition to arm64-only and drop support for arm64_32 devices?
No — Apple Watch Series 9 and later, and Apple Watch Ultra 2 and later all support the arm64 architecture. There are many Apple Watch devices that run watchOS versions your app likely supports beyond that list, so you need to keep the arm64_32 architecture around for those devices. As noted in the announcement, you'll want to use the Standard Architectures build setting for your watchOS app, and that will automatically build the right set of supported architectures for your app, which will include arm64_32 as well as arm64.
If we add support for both arm64_32 and arm64, the binary will almost certainly exceed the 75 MB app size limit, and potentially violate the size constraints for each architecture slice as well.
What size constraints per architecture are you thinking of? The Maximum build file sizes documentation lists such a requirement for iOS apps in the iOS 7 and 8 time frame, but that isn't relevant for anything more recent. Please let me know if you're thinking of something else.
This raises practical concerns about how a dual-architecture watchOS app can remain within the required size limits.
Let's first see if there's actually an issue with your app's size. Start by building and archiving your app with the updated architecture requirements. I'm using the archive process here in Xcode instead of just a regular build because this gives you the version of your app for the App Store, which is what matters for managing the size requirements here.
If you dig inside of the Xcode archive to get to the .app for your watchOS app, what size is it?
Once you have that, then go export your app so that you can get the App Thinning Size Report — Reducing your app’s size explains how to do that. If you look the report, you'll see thinned versions of your app for watchOS, along with the uncompressed size. What's the largest size you see for watchOS?
If neither of those is larger than 75MB, then you don't need to worry. But if either one of those is larger than 75 MB, I would like you to start a bug report with this data so we can discuss it further internally. With this requirement coming in April 2026, it would be good to make us aware of how many apps go over the current limits with adding the arm64 architecture to your app. Please post that FB number here if you file it so I can follow up on that.
Are there recommended techniques specifically for watchOS to reduce binary size when supporting multiple architectures?
I took you down the path of archiving in Xcode in part so you can analyze the size of your existing app based on what we have documented in articles for reducing your app's size:
Every app is different in what takes size, on a spectrum from apps where binaries are the largest file to apps where assets are the largest size. By starting with the unzip file listing in the first article, you'll see what the largest files in your app are, and can then go from there on optimizations.
— Ed Ford, DTS Engineer
