Is there any formula or knowledge about how much Apple's DRM adds to the IPA size when uploading to the store? I heard numbers like 80 mbyte is max. and Apple adds up to 20 MByte, but I fail to find any background information on that. Any help greatly appreciated. We trying currently to crunch assets in our ipa to be at the end under the 100 MB cellular download limit.
Thanks! Martin
The answer depends on a lot of variables, some of which can change on Apple's end. In reality, a compiled IPA should be bigger than the size installed to a specific device by the App Store, because your compiled binary may have @2x and @3x images that will get optimized for the specific device. Also, bitcode will get processed before installation, which should reduce sizes. There are things that may increase the size (Swift libraries, for example).
Your best bet is to use Test Flight to create a build and the see if you are over the limit on any device types. You can get pretty good coverage with a 5s, 6/7, 6+/7+, retina iPad, and non-retina iPad.