iphone backup

At some time in the past you chose to encrypt the backup. At that time you were prompted to enter a backup password — Twice. All backups after that first encrypted backup will be encrypted, but you won’t be prompted again for the password until you go to restore a backup, even if it is years later. If you backed up to a Mac you were given the option to save the password in Keychain, so if you have a Mac launch the Keychain app and look for the backup password. It will be listed as iPhone backup or iOS backup, depending on how long ago you made the backup.

The alternative is to guess the password; if you are like most people and reuse passwords try everything that you might have mentally associated with your iPhone. You get unlimited guesses, and to speed up the process Click Change Backup Password or uncheck Encrypt Backup.

You did set a password if the computer is asking for it. A password is required to encrypt the back up when it contains information from apps such as Health. Unfortunately, without the password, you can't access the backup.