Back up your iPhone to a local drive before you install the iOS 27 beta

If you're going ahead with the beta installation, make sure to back up your iPhone to your Mac or PC. It isn't enough to have an iCloud backup: If your iPhone backs up to iCloud while running the beta, it will overwrite your backup from the current version of iOS. As such, the safer bet is to back up your iPhone to a computer. If you need to downgrade, you can restore your iPhone from this backup and recover your data—minus anything generated after the backup was created. For more information, see Lifehacker's guide here.

Note that this backup is only good for as long as Apple signs (or supports) that version of iOS. Once Apple releases a new official version of iOS and stops signing the version your backup was made to, you won't be able to restore it. (This is me, once again, advising you not to install the developer beta.