Mac storage basics · iPhone and iPad backups and updates
Why encrypt an iPhone backup on my Mac, and does it use more space?
Short answer: Tick Encrypt local backup in Finder. It adds saved passwords, Health and other sensitive data without making the backup much bigger — but you need the password to restore.
In Finder, select the device and tick Encrypt local backup on the General tab. An encrypted backup also includes saved passwords, Wi-Fi settings, Health and other sensitive data that an unencrypted backup leaves out. It doesn't make the backup meaningfully bigger.
Keep the password safe: without it, an encrypted backup can't be restored.