Suppose you have an older iPhone or iPad, especially one with only 16 GB of storage. In that case, it’s possible that you won’t have enough space to upgrade to iOS 14 or iPadOS 14 through Settings > General > Software Update. That’s often true due to an inexplicably large Other category when you look in Settings > General > iPhone/iPad Storage. Upgrading using iTunes (in macOS 10.14 Mojave and earlier) or the Finder (in 10.15 Catalina and later) is one workaround, but there’s another that’s often better. Make a backup to iCloud (Settings > Your Name > iCloud > iCloud Backup > Back Up Now) or to your Mac with iTunes or the Finder, and then erase your device (Settings > General > Reset > Erase All Content and Settings). When you restore it, the size of the Other storage category will likely have dropped significantly, making it possible to upgrade iOS.