There are a few reasons why apps may crash on an iPhone.   First, the app may be overwhelmed with too much information or data and can't keep up with the demands of running in the background.   Second, the app may be using up too much of the device's processing power or storage space, leading to crashes.   Third, if there is an issue with the app's code or design, it may cause crashes.   Finally, if there is something wrong with the device itself (like a hardware issue), Fallen App Syndrome may occur and lead to apps crashing.   These various factors can combine to cause any number of different types of crashes and each poses its own unique set of challenges for developers.   That said, Apple has put in place several robust safety features that help mitigate some common issues and keep users safe.   In particular, background refresh handling ensures that apps always have enough data to run smoothly and recovers from errors quickly so that users never see a degraded experience - even when apps go down for a longer period of time.   Additionally, the use of sandboxing isolates apps from each other so that they can work properly without affecting each other and no user data is shared between them unless explicitly requested to do so by the user.   And finally, secure boot helps ensure that only approved applications are able to start up on an iPhone - ensuring that users will not encounter unauthorized or malicious apps while they're using their iPhone."