Erasing a Mac properly before you sell or hand it on
· 6 min read
Erasing a Mac used to mean wiping the drive and reinstalling from a USB stick. On any reasonably current machine it is one menu item, and the risk has shifted: the common failure now is not leaving data behind but leaving the machine locked to your account, so the next owner has an expensive paperweight.
Order matters more than technique.
Do these in this order
1. Back up, if you have not. Once erased, it is gone. Confirm the backup is complete before continuing, not merely configured. Testing a backup before you need it covers checking rather than assuming.
2. Sign out of everything. This is the step that prevents Activation Lock. Unpairing everything before a Mac leaves you has the full list, and the short version is iCloud, Messages, and any application licensed to the machine.
3. Erase All Content and Settings. System Settings, General, Transfer or Reset. It asks for your password, warns you, and does the rest.
4. Leave it at the setup screen. Do not sign in again. The next owner completes setup with their own account.
Reversing steps two and three is the classic error. Erasing while still signed in to Find My can leave the machine Activation Locked, and unlocking it afterwards requires proof of purchase.
Why Erase All Content and Settings is enough
The instinct to overwrite the drive several times comes from spinning hard disks, where deleted data remained physically present.
Modern Macs store everything encrypted, with the key held in hardware. Erase All Content and Settings destroys that key. Without it the remaining data is not recoverable by any practical means, whatever tools are pointed at it. It takes minutes rather than hours, and it is more thorough than repeated overwriting ever was.
This applies to Apple silicon Macs and Intel Macs with a T2 chip. For older Intel Macs without one, the option may not exist and you erase through Disk Utility in Recovery Mode instead. On those machines, if the drive is a spinning disk rather than an SSD, a security option to overwrite is worth using.
If the option is not there
Older machines, or ones already misbehaving, go through Recovery.
Restart holding Command-R on an Intel Mac, or hold the power button on Apple silicon until startup options appear, then choose Options.
In Recovery, open Disk Utility, select the internal volume, and erase it as APFS. Then quit Disk Utility and choose Reinstall macOS. What Recovery Mode is covers getting in.
The reinstall needs internet and takes a while. Leave the machine plugged in.
What people forget
Paired Bluetooth devices. A keyboard or mouse still paired will connect to the erased Mac and confuse the new owner. Unpair them first.
Time Machine backups on a shared drive. If the drive stays with you, the backups are yours to keep. If it goes with the Mac, it holds a full copy of everything you just erased.
External drives connected during the erase. Disconnect them. Erasing the wrong volume is not recoverable.
Licences tied to the machine. Some applications allow a limited number of activations. Deauthorise on the old machine while you still can.
The recovery key. If you had FileVault on, the recovery key for this machine is now meaningless. Delete it from wherever you stored it so it does not clutter your records.
Handing a Mac to someone you know
Slightly different from selling. The temptation is to leave your account and just add theirs, which is a mistake: your files stay on the machine, your account remains an administrator, and the arrangement is awkward to unwind later.
Erase it properly and let them set it up as their own. If they want your files, copy the specific ones to a drive first.
If it is going to someone who will find setup difficult, do the erase, then walk them through the initial setup rather than doing it for them under your account. Setting up a Mac for someone who is not comfortable with computers covers doing that well.
Selling it
Two practical notes.
Serial numbers are worth removing from listing photos. They are not secret exactly, and they can be used to make a support enquiry look legitimate.
Do not accept a request to reinstall a specific version, sign in to any account, or install anything for a buyer. Hand it over at the setup screen.
Questions
Does erasing remove the macOS version? Erase All Content and Settings keeps the installed version. A Recovery erase and reinstall may install a different version depending on how you started Recovery.
How long does it take? Erase All Content and Settings, a few minutes. Erase and reinstall through Recovery, anywhere from thirty minutes to a few hours depending on the download.
What if I already erased while signed in? Sign in to icloud.com, go to Find My, find the device, and remove it from your account. That clears Activation Lock remotely.
Can the buyer recover my files afterwards? Not from a properly erased modern Mac. The encryption key is destroyed, so what remains is not decryptable.