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Can't install an app on an iOS device? Things to check

Apple doesn't provide explicit error messages when installing apps on devices. It can be quiet difficult to understand what could have gone wrong.

Behaviors

iOS install popup did not appear

After tapping the "Install" link on the Diawi installation page, if the iOS popup "Diawi would like to install…" did not appear, check that you don't already have the same app installed from the AppStore. If an app with the same bundle identifier is already installed on the device from the AppStore, nothing will happen. This is a security behavior added by Apple in iOS 8+ to prevent a malicious developer from overwriting a real app with another one.

Delete the app installed from the AppStore to be able to install the testing one from Diawi.

Nothing seems to happen

The popup appeared, but after tapping the "Install" button of the popup, nothing seems to happen: check the device's home screen as the installation should be in progress in the background. Since iOS 8+, app installation if performed in the background on the device's home screen and Safari doesn't show anything special, however the icon can be found on the home screen and a progress indicator shows the installation progress.

Untrusted Enterprise Developer popup

Starting from iOS 9+, the developer of an Enterprise signed app (in-house mobileprovision) has to be trusted by the user of the device, otherwise a popup will appear and prevent from using the app.

On iOS 9.0/9.1, this can be done in: Settings > General > Profiles > tap on the developer's profile, and tap on Trust. On iOS 9.2+, this can be done in: Settings > General > Device Management > tap on the developer's profile, and tap on Trust.

Unable to download app popup

If an "Unable to download app" popup appears after some time, first check the internet connection, and be sure that the device is not behind a firewall that may prevent downloading .ipa files (as this happens a lot in enterprise firewall configurations).

Sadly, iOS won't give any detailed information on what went wrong here. As a user, Diawi provides information on the installation page about the most common checks. As a developer, a detailed list of checks can be found below.

Most common installation issues are: * expired provisioning profile
* device UDID not in the provisioning profile
* incompatible device (check minimum iOS version, device family, required device capabilities and supported architectures)

A few things to check as a developer

If you have uploaded an app to Diawi and can't install it on some of your devices, here are a few things to check:

  • device's UDID must be in the provisioning profile built into the app by xcode
  • device's UDID must not start with "fffffff..." (if it is, then it is fake)
  • you are building a Release version of your app
  • the device is not behind an enterprise firewall preventing app installation

You may also try to drag&drop the app into iTunes and sync your device: it should install the app, otherwise it is not valid.

More detailed explanations

UDIDs in the provisioning profile

Apple rules regarding app installation also apply when using Diawi: if you are using a Development or Ad-hoc provisioning profile, devices' UDIDs must be added to the provisioning profile used to sign your app. In-house builds with an Enterprise Apple account don't require registering UDIDs.

Since xcode 4, the .mobileprovision file is embedded into the .app/.ipa file when compiling. When in doubt about which version has been used by xcode, you may simply unzip the .ipa file, then right-click Show package content on the .app located inside the Payload folder and look for the embedded.mobileprovision. The file can be opened with a text editor (TextMate, Sublime Text, Atom, ...): contains some XML/plist contents with the list of UDIDs.

XML/plist data inside the .mobileprovision looks like this:

<key>ProvisionedDevices</key>
<array>
    <string>37149a037f1..................................3c0078</string>
    ....
</array>

Also, Diawi displays this list on the installation page and checks if the user's device UDID is inside that list.

Valid UDIDs

UDIDs are string of 40 hexadecimal characters ([0-9a-f]{40}).

Device's UDID must be retrieved using iTunes or a webapp like m.diawi.com: those UDIDs are known to be valid.

For some time, it was possible to get the device's UDID using a native API provided by Apple and integrated in some apps available on the AppStore. However, this API has been deprecated in iOS 7 and instead provides a "fake" UDID starting with ffffff.... Those UDIDs are not valid and can't be used to identify a device and install apps on it.

Built architectures

When building iOS apps, you may be targeting one or more of the available architecture (armv6, armv7, arm64). With the Debug configuration in xcode, the default setting is to build only the "current" architecture (for faster compilation), which may prevent the app from running on other/older devices.

Current architectures and their compatibility:

  • armv6: iPhone 2G+, iPod touch 1st gen.+
  • armv7: iPhone 3GS+, all iPads, iPad mini 1, iPod touch 3rd gen.+
  • armv7s: iPhone 5+, iPad 4+, iPad mini 1, iPod touch 3rd gen.+
  • arm64: iPhone 5s+, iPad Air+, iPad mini 2+, iPod touch 6th gen.+

(Source: List of iOS devices on Wikipedia)

Newer devices are so far compatible with older architectures: an iPad Air, arm64, can run an armv7 built app, but not the opposite.

With the Release configuration, all the active/current architectures will be built and the app will work on all the targeted devices. As of Xcode 6/7, the default is armv7+arm64 (armv7s is not really needed: it's exclusion could be that it doesn't provide enough enhancement compared to armv7 while it might be adding extra file size).

This document is available on our public GitHub repository. Feel free to fork and send pull requests if you find any interesting information to add.