Which drive
An external SSD or HDD with 2–3 times the space used on your MacBook. SSDs are faster and sturdier to carry; HDDs are cheaper for a copy that stays at home. Time Machine offers to format the drive during setup.
Turning it on
- Plug in the drive.
- Open System Settings → General → Time Machine.
- Click “Add Backup Disk”, choose the drive and turn on backup encryption.
- The first backup takes a while — leave the Mac on charge overnight.
How it works
While the drive is connected, Time Machine backs up every hour and keeps older versions: hourly for a day, daily for a month, weekly while space allows. You can bring back a file as it was a week ago.
Restoring
A single file — open its folder in Finder, start Time Machine from the menu bar and pick the date. A whole Mac — when setting up a new one or after a repair, choose to transfer from a Time Machine backup.
A second copy in the cloud
A drive at home will not survive theft or fire. Documents and photos in iCloud Drive and iCloud Photos are your off-site copy — together with Time Machine that is the 3-2-1 rule.