Time Machine Backup:
Set It & Forget It

The only computer problem that can't be undone

In this line of work you get used to fixing things. Slow Macs speed up. Frozen apps quit. Wi-Fi comes back. Forgotten passwords get reset. Almost every problem that lands on my calendar has a way out — except one. When the files are gone and there's no copy anywhere, there is nothing I can do. No software, no service, no fee fixes it. That's the whole reason this guide exists.

And notice how files actually disappear: a drive that quits with no warning noise, a laptop left in an airport, a glass of water, or — by far the most common — a folder deleted by hand and emptied from the Trash before anyone noticed. Only one of those is a computer failure. The rest are ordinary life. So I don't sell backup as protection against some rare disaster. It's protection against Tuesday. Everything below is written for macOS Tahoe 26; if your Mac is a version or two behind, the same words sit in the same places.

The 60-second version

• Buy one external drive. Apple's own advice is a drive with at least twice the storage capacity of your Mac. Figure about $70 to $150.
• Plug it in and say yes. Apple menu > System Settings > General > Time Machine > Add Backup Disk. That's the entire setup.
• Expect it to offer to erase the drive. That's normal — and it's why you buy a fresh drive rather than the one with the vacation photos on it.
• The first backup takes hours, not minutes. Apple doesn't promise a number and neither will I. You can keep using the Mac while it runs.
• Then it runs itself. Hourly backups for the past 24 hours, daily for the past month, weekly for all previous months. The oldest ones drop off when the drive fills.
• Learn one recovery trick. Getting a deleted file back takes about ninety seconds once you've watched it done.

Setting it up, step by step

1. Plug the drive into your Mac. If an icon appears on the desktop, the Mac sees it.
2. Click the Apple menu in the top-left corner, then System Settings.
3. Click General in the list down the left side.
4. Click Time Machine on the right.
5. Click Add Backup Disk — or the + button, if that's what you see.
6. Click your drive in the list, then click Set Up Disk.
7. Answer the two questions — erasing and encryption (both explained below).
8. Done. Your Mac starts backing up on its own within a minute or two. While you're in System Settings, go to Control Center, scroll to Time Machine, and choose Show in Menu Bar so you can see it working.

Choosing a drive without overthinking it

Time Machine is free; the drive isn't. Apple's sizing rule is simple — use a storage device with at least twice the capacity of your Mac. A Mac with 1TB inside wants a 2TB backup drive. The extra room is what lets it keep months of history instead of just yesterday. As of mid-2026 that's roughly $60–$90 for 1TB, $80–$140 for 2TB, and $110–$200 for 4TB, and prices do move. A plain USB hard drive is fine and cheapest; an SSD costs more but is quieter and survives being knocked off a desk, which matters for a laptop drive. Check the plug before you buy — newer Macs use USB-C and plenty of drives still ship with the older rectangular cable. And give the drive one job: Apple says to use your Time Machine backup disk only for Time Machine backups, not for storing other files.

The two questions setup asks you

“Erase this disk?” — Time Machine wants the drive in Apple's own format, and setting that up wipes whatever is on it. Brand-new drive out of the box? Say yes. Drive with your files already on it? Stop, copy those files elsewhere first, or better yet buy a second drive. Erasing is permanent. “Encrypt backup?” — this locks the backup with a password so a stranger who picks the drive up can't read your files. The trade-off is real and Apple states it plainly: you'll need that password if you ever restore, and there is no back door. My honest advice — encrypt any drive that travels or leaves the house, write the password down on paper, and for a drive that lives permanently behind an iMac, unencrypted is a defensible choice.

How the schedule works, and what falls off the end

Apple's schedule, stated exactly: hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for all previous months — and the oldest backups are deleted when the backup disk is full. Read that as a shape: the recent past is detailed, the distant past is sketched. Deleted something an hour ago? You can have the version from an hour ago. Deleted it two years ago? Maybe a weekly snapshot survives, maybe the drive has since filled and rotated. Since macOS Ventura you can change how often it runs — Time Machine menu > Open Time Machine Settings > Options > Back up frequency — and that same Options panel is where you exclude folders you don't want backed up. I'd leave the frequency on automatic. I've never once been glad a Mac backed up less often.

Getting one deleted file back

1. Make sure the backup drive is plugged in.
2. Open the folder the file used to live in — Documents, say. (If it was on the desktop, skip this step.)
3. Click the Time Machine icon in the menu bar and choose Browse Time Machine Backups. Or press Command-Space, type Time Machine, and press Return. Older versions of macOS called this Enter Time Machine — same screen.
4. Your folder appears stacked into the distance with a timeline down the right edge. Use the arrows, or click a date on the timeline, to travel back until your file reappears.
5. Click the file once to select it, then click Restore. It returns to exactly where it was.
6. Bonus trick: in many Apple apps you can open a document and choose File > Revert To > Browse All Versions to pull back an earlier draft without leaving the app.

Restoring an entire Mac

This is the big one — a new Mac, or one that came back from repair wiped clean. The tool is called Migration Assistant. On a brand-new Mac, plug your Time Machine drive in before you start the setup questions; when it asks whether you want to transfer information, choose the Time Machine backup, pick the date you want, enter your encryption password if you set one, and walk away. Apple's own warning is worth repeating: large transfers might take hours and might seem to pause occasionally. Let it finish. On a Mac that's already set up, open Migration Assistant by hand from Spotlight. If the Mac won't start at all, macOS Recovery gets you in, and Migration Assistant offers your backup after macOS is reinstalled. My Moving to a New Mac guide walks through the whole day.

Time Machine vs iCloud — you want both

This is the most useful sentence I know on the subject: sync is not a backup. iCloud keeps your devices matching and protects you from fire and theft, because it's off-site. But delete a file on one device and it deletes everywhere, with about 30 days to change your mind. Time Machine is the opposite — it's your undo button and the only thing that can rebuild a whole Mac including apps and settings, but the drive is sitting right next to the computer, so it burns in the same fire. Use both. For most households that's three copies of anything you'd hate to lose, on two kinds of storage, with one copy somewhere else — my 3-2-1 Backup Plan guide lays out the rest, and my Photo Backup guide covers the files people actually grieve.

The two-minute check that keeps it honest

A backup nobody looks at is a promise nobody has checked. Once a month — bill-paying day is a fine anchor — click the Time Machine icon in the menu bar and read the top line. It shows either a backup in progress or the date and time of the latest backup. Is that date recent? For a desktop, within a day. For a laptop you plug in weekly, within a week. If it's old, plug the drive in and choose Back Up Now, then watch it start. That single habit is the difference between a backup and the idea of a backup. The most common failure I find isn't broken software — it's a drive that got unplugged for a trip in March and never went back in.

What's in the 27-page PDF

• Why this is the one computer problem that can't be undone — the four ways files really disappear
• The 60-second version: six checkboxes that cover the whole topic
• What Time Machine actually does, and the three things it doesn't
• Choosing a drive — the size rule, a price table, and which kind to buy
• Setting it up: System Settings > General > Time Machine, step by step
• The two questions — erasing the drive, and whether to encrypt
• The first backup: how long, what to expect, and the easy way to do it
• Where the drive lives — desktop vs laptop routines, and ejecting safely
• Hourly, daily, weekly — the schedule, changing it, and excluding folders
• The two-minute monthly check, plus the red flags worth a second look
• Getting one file back, older versions of a document, and restoring an entire Mac
• Time Machine vs iCloud, photos specifically, troubleshooting, ransomware and backup scams, a fridge checklist, a glossary, and a fill-in cheat sheet

Why I wrote this

I'd call this the highest-value hour anybody can spend with their computer. Not the fastest, not the most exciting — the most valuable. Everything else in tech is an inconvenience when it goes wrong; losing forty years of photographs is a different kind of loss, and it's the one that's completely preventable. What frustrates me is that the fix already came with the machine. Nobody ever showed folks the switch. So I wrote this one as a printable handout to keep in the drawer next to the Mac — set it up once when nothing is wrong, check the date on the first of the month, and the day something does go wrong turns into an errand instead of a tragedy. — Bill