Time Machine
Keep your files safe — and recoverable
Apple provides a completely free, easyto-use, powerful backup utility as part of macOS. So it’s baffling that many people don’t turn it on. There isn’t even the excuse that it’s too technical — to get started with Time Machine, all you have to do is connect an external drive to your Mac. You’ll be asked whether you want to use the drive with Time Machine. Simply click “Use as Backup Disk.” Congratulations, you’ve just made your first step to securing your files. Easy, wasn’t it?
In fact, pretty much everything about Time Machine is user-friendly, even if aspects of its interface are esoteric (like maybe the “time travel” concept — see our walkthrough on restoring a file). When Time Machine’s preferences open after you get things going, you’ll see that it’s actually very straightforward. You can toggle whether Time Machine backs up automatically — we recommend you leave that on, unless you have a very good reason not to. You can select a new Time Machine disk. You can also exclude specific items from your backup — to do this, click the Options button. You’ll rarely want to add anything to the exclusion list, but if for example you have a Mac with multiple storage volumes and want to back up only one of them, you can add the others to the list.
Your initial backup might take some time, but after that, any future backups will be incremental, saving only whatever has changed since the last backup. Unless you’re triggering a backup manually (from Time Machine’s menu bar icon), backups will happen roughly hourly. As Time Machine’s System Preferences pane notes, the previous 24 hours of hourly backups are kept complete, along with daily backups for the previous month and weekly backups for all previous months — provided space allows. If it doesn’t, the oldest backups are deleted. If that’s not enough, Time Machine will alert you that it needs more space. At that point, you can either exclude more items (a bad idea) or connect a bigger backup drive (much better).
Under the hood
If you look at the top level of your Time Machine drive in Finder, you’ll see a special folder called Backups.backupdb, which is the place Time Machine stores its backups, organized in a special way. It’s best to avoid touching the contents of that folder, but if you need to start using a bigger drive
and want to keep your backup history, follow the instructions Apple gives at bit.ly/newtmdisk.
If your Time Machine drive isn’t available (say, if the external drive happens to be disconnected or switched off), Apple’s backup system continues doing its thing. If your Mac has enough space, local snapshots are saved (and can have files recovered from them). The key there is whether there’s enough space — if you don’t have a great deal of free space on your Mac, do not rely heavily on this feature, because local snapshots are stored for 24 hours at most before being deleted — less if your Mac needs room for something else.