Apps without the Store
Q Is it possible to install an app that isn’t on the App Store? I have tried adding a .ipa file to iTunes on my Mac but get an error. Dimitri Molchanov A Where does this app come from? If it is an old app that’s been removed from the store, you may be able to restore it provided that you had previously installed it and it appears in your list of purchased apps in iTunes. But if it’s a random .ipa file you’ve found on the web then you can’t install it without jailbreaking your device. Nor should you, since there is no way to verify its provenance.
Apple’s approval process ensures the apps on its store are reliable, free from malicious code and offensive material.
If the app is something you have written yourself, on the other hand, then you can side-load it onto your device by enrolling in the Apple Developer Program (developer.apple.com/programs).