How to Backup Mac Before Upgrade

Upgrading macOS is usually smooth, but a backup is your safety net if something goes wrong during installation or if an app you rely on isn’t compatible with the new system. This guide walks you through creating a full backup using Time Machine and an optional bootable clone, so you can restore your Mac exactly as it was if needed.

What You’ll Need

• An external drive with at least as much storage as your Mac’s internal drive (more is better). It will be erased, so make sure it doesn’t contain anything you need.
• A stable power connection (plug in your Mac if it’s a laptop).
• macOS 10.13 High Sierra or later for the Time Machine steps (most Macs that can upgrade already have this).
• Optional: a second external drive if you want a bootable clone in addition to a Time Machine backup.

Step-by-Step

1. Connect your external drive to your Mac. If it’s a new drive or one you’ve used for other things, you’ll need to erase it first. Open Disk Utility (in /Applications/Utilities/), select the drive in the sidebar, click Erase, choose Mac OS Extended (Journaled) or APFS as the format, and GUID Partition Map as the scheme. Click Erase again to confirm.
2. Turn on Time Machine. Go to System Settings (or System Preferences on older macOS) > General > Time Machine. Click Add Backup Disk and select your external drive. Time Machine will start backing up automatically.
3. Wait for the first backup to finish. The first backup copies everything, so it can take hours. You can check progress by clicking the Time Machine icon in the menu bar (it looks like a clock with a circular arrow). Make sure it says “Latest backup: Today” or shows a completion time.
4. Verify the backup. Open Time Machine from the menu bar and click Enter Time Machine. You should see a timeline on the right and your files in the window. Navigate to a few folders to confirm your files are there. Exit Time Machine.
5. Create a bootable clone (optional but recommended). If you have a second external drive, you can make a bootable copy using SuperDuper or Carbon Copy Cloner (both have free trials). These apps copy your entire system to the drive, making it bootable. Follow the app’s instructions to clone your internal drive to the external drive.
6. Disconnect the backup drive once you’re confident the backup is complete. Keep it somewhere safe. You don’t need it connected during the upgrade, but you should have it handy in case you need to restore.
7. Start the upgrade. Go to System Settings > General > Software Update and click Upgrade Now (or use the App Store). Follow the on-screen instructions. Your Mac will restart several times.

Common Mistakes

• Using a drive that’s too small. If the external drive has less space than your internal drive, Time Machine will only back up part of your data, and you might not notice until you try to restore.
• Not erasing the drive first. If the drive has an old format or partition scheme, Time Machine might refuse to use it or back up incorrectly. Always erase it with Disk Utility first.
• Assuming Time Machine is on. If you never configured Time Machine, it’s not backing up. Check the menu bar icon to make sure it’s actually running.
• Backing up to the same drive you’re upgrading. You cannot back up to the internal drive. It must be external.
• Disconnecting during the backup. If you unplug the drive mid-backup, the backup may be incomplete or corrupted. Wait for it to finish.

Tips

• Keep a second backup. Time Machine is great for file recovery, but a bootable clone lets you start up from the external drive immediately if your internal drive fails. Use both if you can.
• Use a wired connection. If you’re backing up over a network (Time Machine supports network drives), it’s slower and less reliable than a direct USB or Thunderbolt connection. Use a cable if possible.
• Check for app compatibility. Before upgrading, look up whether your most important apps support the new macOS version. Some older apps may not work, and a backup won’t fix that.
• Keep the backup after upgrading. Don’t delete your backup immediately after a successful upgrade. Keep it for at least a month in case you discover a missing file or want to downgrade.
• Use the built-in migration tool. After upgrading, you can use Migration Assistant to restore from your Time Machine backup if needed, but you usually won’t need to.

Troubleshooting

• Time Machine says the drive is not compatible. Re-erase the drive in Disk Utility, making sure to choose GUID Partition Map and a supported format (APFS or Mac OS Extended). If the drive is very old, it might not work with APFS; use Mac OS Extended instead.
• The backup is taking forever. The first backup is always the slowest. If it seems stuck, check that the drive is connected properly and that your Mac isn’t going to sleep (adjust Energy Saver settings to prevent sleep during backup). You can also pause other heavy tasks.
• Time Machine doesn’t show the drive in the list. Make sure the drive is mounted (visible on the desktop or in Finder). If not, unplug and replug it. If it still doesn’t appear, try a different USB port or cable.
• You see “Backup failed”. Check the drive’s free space. If it’s full, Time Machine will fail. Delete old backups (in Time Machine preferences, you can exclude large folders or delete old snapshots) or use a larger drive.
• You can’t restore from the backup after upgrading. If you need to restore, restart your Mac and hold Command + R to enter Recovery Mode. From there, choose Restore from Time Machine Backup and select your drive. If that doesn’t work, try booting from your clone (hold Option at startup and select the external drive).

Frequently Asked Questions

Do I really need a backup before upgrading?

Yes. While upgrades rarely fail, they can, and a backup ensures you don’t lose photos, documents, or settings. It also lets you downgrade if the new macOS causes problems.

Can I use iCloud as my backup?

iCloud syncs files, but it’s not a full backup. It doesn’t include your system files, apps, or settings. Use Time Machine or a clone for a complete backup.

How long does a Time Machine backup take?

The first backup can take several hours, depending on how much data you have and the speed of your drive. Subsequent backups are much faster because they only copy changes.

What if I don’t have an external drive?

You can back up to a network drive (like a NAS) if you have one, but it’s slower. Alternatively, you can at least copy your Documents, Desktop, and Photos folders to a cloud service or another computer, but this is not a full backup.

Can I upgrade without a backup if I have nothing important?

Technically yes, but it’s risky. Even if you think you have nothing important, you might forget about a project or photos. A backup is cheap insurance.

Should I keep the backup after the upgrade?

Yes, keep it for at least a few weeks. If you discover a missing file or decide you don’t like the new macOS, you can restore or downgrade.

Related

• GitHub CLI Commands: The Essential Guide
• Customize Safari Settings for Individual Websites
• Web Hosting Pricing Models Explained