Part 2: Backup iPhone to external hard drive on Macīefore manually backup iPhone to external hard drive, please make a copy of original backups that have been ever saved on the default backup location.
In order to release the disk space the backup files occupy, you can backup iPhone to external hard drive instead. Usually while you back up iPhone through iTunes on Windows or Mac, the backup file will be automatically saved in default location on the limited disk space. How to Backup iPhone to External Hard Drive on Windows and Mac