How can I free enough storage to install an iPhone update?

A backup followed by erasing and restoring the phone can clear unusually bloated temporary or system data, but that should be a last resort. Make a verified iCloud or computer backup first, and don’t erase the device unless you’re sure the backup contains everything important.

The update may need more than the advertised 12 MB because the phone needs temporary working space to unpack and install it. Check the iPhone model, current iOS version, total storage capacity, and the storage breakdown before deleting anything else.

If you have access to a Mac or Windows PC, try updating the iPhone through Finder or iTunes. Installing the update from a computer usually requires less free space on the phone than updating directly over the air. It would also help to check Settings > General > iPhone Storage to see whether System Data or another category is unusually large.

Temporarily removing a large game or another app you can easily reinstall is usually a quick fix. You can download it again after the update, as long as its data is backed up or synced.