Earlier this month, I wrote about How to Restrict Your iOS App to Modern Hardware. One of the suggestions I made was to use the UIRequiredDeviceCapabilities key in your Info.plist file to make your app run only on devices with armv7 CPUs. Several people contacted me afterwards to tell me that this approach only works for new apps.

You heard that right: when updating an app, it seems you cannot add new restrictions to the Required Device Capabilities. One developer who contacted me said he has been fighting with this for more than 2 years, and all due to the simple mistake of omitting the “telephony” requirement in version 1.0 of his app.¹

Automatic Rejection by Xcode’s Validator

According to the feedback I got, this is not even an issue that could be discussed during the app review process. Instead, it seems that the automatic validation service that Apple has integrated into Xcode will reject any update with more restrictive UIRequiredDeviceCapabilities than the earlier version before you can even upload it to iTunes Connect.

How About Not Changing the Deployment Target for Your App’s Lifetime?

I think this is a very bad rule on Apple’s side and I wonder how it can be reconciled with other Apple policies regarding app updates. Ultimately, raising the required device capabilities is equivalent to increasing your app’s Deployment Target², something that Apple has no problem with in an app update.

One could argue that from the perspective of the users, a minimum OS version is easier to communicate than changed hardware requirements but I find that unconvincing. If anything, changed hardware requirements should be easier to understand than changes on the software side since every user knows that hardware cannot be updated while it’s a lot harder to grasp why an old device should not be able to run a new OS version. And Apple does a bad job of communicating changed OS version requirements anyway so it strikes me as odd that they should care so much about the hardware side of things.

In addition, there are some hardware features Apple actively pushes, encouraging developers to adopt them in their apps. The prime example is probably the non-backwards compatible OpenGL ES 2.0. During the recent iOS 5 Tech Talks, Apple actively rallied developers to switch to OpenGL ES 2 to make their apps better. But how is a developer supposed to switch from OpenGL ES 1.1 to 2.0 if he is not permitted to add the corresponding UIRequiredDeviceCapabilities key to its updated app? In that case, he would be forced to increase the Deployment Target to iOS 4.3+ (all devices that run iOS 4.3 also support OpenGL ES 2.0) and his Info.plist would not reflect the correct hardware requirements anymore. Looks like a bad workaround to me.

Downgrades are Possible

It is worth noting that the other way – lowering the required device capabilities – is indeed possible. One developer told me that they had no problems when they removed a requirement from their app.

Please File a Bug Report

If you also think this is a bad policy that Apple should change, please file a bug report. Feel free to refer to the bug ID under which I reported the problem: rdar://10623835.