How to Prepare Your Mac for a macOS Upgrade

Upgrading to the latest macOS is exciting, but a little prep work prevents data loss, broken apps, and a stalled install. This guide walks you through the essential steps—backing up, checking compatibility, freeing space, and more—so the upgrade goes smoothly. You’ll need about 30–60 minutes and a stable internet connection.

What You’ll Need

A Mac that supports the new macOS version (check Apple’s compatibility list)
An external drive (or Time Machine backup location) with at least as much free space as your used data
Stable internet connection (Wi-Fi or Ethernet)
Apple ID and password (for signing in after upgrade)
At least 20–30 GB of free storage on your Mac (more if you have large apps)

Step-by-Step

Check compatibility. Go to the Apple menu > About This Mac, note your model and year. Visit Apple’s macOS compatibility page to confirm your Mac can run the new version. If unsupported, stop here.
Back up your Mac. Connect an external drive, go to System Settings > General > Time Machine, and select the drive. Click Back Up Now and wait until the backup finishes. Alternatively, use Carbon Copy Cloner or SuperDuper for a bootable clone. Verify the backup by opening a few files.
Update your current apps. Open the App Store > Updates tab and install all pending updates. For third-party apps, check each developer’s site for macOS compatibility. Uninstall apps you no longer use—this frees space and avoids conflicts.
Free up storage space. Go to Apple menu > About This Mac > Storage. Click Manage to see recommendations. Empty the Trash, delete old downloads, and move large files (movies, archives) to an external drive or cloud. Aim for at least 20–30 GB free, but more is better for large upgrades.
Disconnect non-essential peripherals. Unplug external drives, hubs, printers, and other accessories except your mouse/keyboard and power adapter. This prevents driver conflicts during installation.
Ensure power and internet. Plug in your Mac (if it’s a laptop) and connect to a reliable network. Avoid using a VPN or proxy during the download/install.
Download the installer. Open System Settings > General > Software Update. Click Upgrade Now (or the upgrade button). If it’s not there, search the App Store for the macOS name (e.g., “Sonoma”) and click Get. Wait for the download to complete—this can take a while.
Run the installer. Once downloaded, the installer opens automatically. Click Continue and follow the on-screen prompts. Agree to the license, select your startup disk (usually Macintosh HD), and click Install. Your Mac will restart and show a progress bar. Do not interrupt it.
Complete setup. After installation, your Mac restarts. Sign in with your Apple ID and password. You may be asked to set up Siri, iCloud, or other services—choose what you want. Check that your files and apps are present.

Common Mistakes

Skipping the backup. Even if the upgrade usually goes fine, a power outage or software glitch can corrupt your data. Always back up first.
Not checking app compatibility. Some older 32-bit apps won’t run on newer macOS versions. Check with the developer or use a tool like Go64 (for Catalina and earlier).
Ignoring storage space. Running out of space mid-install can cause the upgrade to fail. Free up more than the minimum.
Upgrading on a weak internet connection. A dropped connection can corrupt the installer. Use a wired connection if possible.
Forgetting to disable FileVault temporarily. FileVault encryption is fine, but if you have a firmware password set, disable it before upgrading—otherwise the installer may not proceed.

Tips

Create a bootable installer. If you have a 16 GB USB drive, you can create a bootable installer using Terminal commands. This lets you do a clean install if needed.
Use a clean install for major upgrades. If you’re going from macOS Monterey to Sonoma, consider erasing your disk and installing fresh, then migrating your data. This avoids leftover clutter.
Keep your Mac plugged in. For laptops, ensure the power adapter is connected—the installer may refuse to run on battery.
Check your disk health first. Run First Aid in Disk Utility (Applications > Utilities > Disk Utility) to check for errors before upgrading.
Wait a few weeks. If you rely on your Mac for work, consider waiting for the first point release (e.g., 14.1) to avoid early bugs.

Troubleshooting

Installer says “macOS could not be installed.” Restart your Mac, then try again. If it persists, check your storage space and ensure you’re connected to the internet. You may need to download the installer again via the App Store.
Upgrade gets stuck on a black screen or progress bar. Wait at least 30 minutes—some upgrades take a while. If nothing changes, force restart by holding the power button, then try again. If it fails repeatedly, boot into Safe Mode (hold Shift at startup) and retry.
Your Mac restarts to a login screen but loops. Try resetting the NVRAM (on Intel Macs: restart and hold Option+Command+P+R until you hear the chime twice). On Apple silicon, just restart.
Apps are missing or broken after upgrade. Reinstall them from the App Store or developer’s site. Some apps may need updates—check for patches.
Wi-Fi doesn’t work after upgrade. Go to System Settings > Network, turn Wi-Fi off and on. If that fails, delete the Wi-Fi service and re-add it (System Settings > Network > Details > Remove Service, then add it back).
You can’t sign in with your Apple ID. Ensure you’re connected to the internet. Try resetting your password via iforgot.apple.com. If the issue persists, contact Apple Support.

Frequently Asked Questions

Do I need to back up before upgrading? Yes, absolutely. A backup protects your files if something goes wrong during installation.
How much free space do I need? Apple recommends at least 20–30 GB, but having 50 GB or more is safer, especially for large upgrades.
Will I lose my files during the upgrade? No, an in-place upgrade preserves your files and settings. However, a clean install (erasing the disk) will remove everything, so always back up first.
Can I downgrade back to the previous macOS? Yes, but it’s complicated. You’ll need to erase your disk and reinstall the older version from a bootable installer, then restore from backup. Do it within a few days if you’re unsure.
Why is my Mac slow after the upgrade? Spotlight re-indexing and other background tasks can slow things down for a few hours. Give it time. If it persists, check for updates and restart.
What if my Mac is too old for the new macOS? You can’t upgrade, but you can continue using the current version. Apple may still provide security updates for a few years. Consider a new Mac if you need the latest features.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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