To create backups with Time Machine, all you need is an external storage device. After you connect the storage device and select it as your backup disk, Time Machine automatically makes hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for all previous months. The oldest backups are deleted when your backup disk is full.
Connect one of the following external storage devices, sold separately. Learn more about backup disks that you can use with Time Machine.
After you select a backup disk, Time Machine immediately begins making periodic backups—automatically and without further action by you. The first backup may take a long time, but you can continue using your Mac while a backup is underway. Time Machine backs up only the files that changed since the previous backup, so future backups will be faster.
To start a backup manually, choose Back Up Now from the Time Machine menu in the menu bar. Use the same menu to check the status of a backup or skip a backup in progress.