Upgrading to a new version of iOS isn’t an easy task if you’ve got a device with 16GB or storage or less. Starting with iOS 9 though, Apple’s going to help you free up space by automatically deleting your apps. But don’t worry, it’ll put them right back after updates are done.
This is what the notification looks like if you don’t have enough space:
iOS 8 upgrades required over 4GB of free space in order to perform updates, which caused the adoption of the mobile operating system to lag behind iOS 7. With iOS 9, updates will only be about 1.3GB in size, but it can still be tough for many users to free up that much space, especially if they’re not syncing to iTunes to manage storage manually.
Apple revealed at WWDC that iOS 9 will require less free space to update now that devices don’t have to download and unpack software updates. There’s also new notification options for upgrades that let you update your device when you sleep or use it least.