The erase takes five minutes and hardly anybody gets that part wrong. What people get wrong is the order of the steps around it, and unlike the erase itself, the order cannot be put right afterwards.
Every meaningful answer on this page forks on the model, so establish it before anything else. Apple menu, About This Mac, and read the chip or processor line. There are three generations in circulation and they behave completely differently when erased. Apple Silicon machines — anything with an M-series chip — encrypt their storage in hardware as a matter of course. Intel Macs from roughly 2018 to 2020 carry the T2 security chip and do the same. Intel Macs from 2017 and earlier have neither, and on those an erase means something much weaker than most people assume.
That single fact decides three separate things: which erase procedure you follow, whether anything at all could be retrieved afterwards, and whether the machine is worth sending here if you later realise you wiped the wrong one. It is thirty seconds of checking that prevents most of the bad outcomes described below.
The first is getting the files off, and specifically getting them somewhere you have actually opened. A Time Machine disk that has never been restored from is an assumption with a schedule attached; mount it and look for the folders you care about, by name, on screen. Then sweep up everything that lives outside the obvious places — the desktop, Downloads, local mail archives, licence keys typed into a note years ago, anything sitting in a folder synced to a service you are about to sign out of.
The second is detaching the machine from you, and this is the step that generates the awkward phone calls. Sign out of Apple ID, iCloud and Messages, and switch Find My off. On Apple Silicon and T2 machines, leaving Find My on leaves Activation Lock enabled, which means the next owner reaches the setup assistant, is asked for your Apple ID password, and has a paperweight until you supply it — a wipe does not clear it, because the lock lives on Apple's servers and not on the disk. Deauthorise the machine in the Music or iTunes app if you have ever bought anything, and unpair the Bluetooth keyboard, mouse or trackpad so they do not follow the Mac out of the house.
On any M-series Mac, and on any Intel model carrying a T2, the entire operation is a single menu item. Open System Settings, choose General, then Transfer or Reset, and the option you want is Erase All Content and Settings. It handles the sign-out from Apple services, strips the data and the settings, and leaves the machine sitting at the setup assistant. No manual reinstall of macOS is needed and none should be attempted.
It is worth understanding what happens underneath, because it explains why nothing ever comes back. Storage in these machines has been encrypted since it left the factory, with the keys held inside the Secure Enclave. Erasing does not work through your files rewriting them one by one. It throws the keys away, and the flash is left holding ciphertext that nothing anywhere is capable of turning back into a photograph. That is genuinely final: not difficult, not expensive, not a matter of finding the right laboratory. Excellent news when you are selling the machine on. A very short conversation when you have just wiped the wrong one.
Without a T2 there is no single control, so everything runs through macOS Recovery. Restart the machine holding Command and R. Once Disk Utility opens, the first thing to change is in the View menu — switch on Show All Devices, which reveals the physical drive sitting above the volumes it carries. It is that top-level device you erase, not the volume underneath. Pick APFS if the hardware is reasonably modern; Mac OS Extended (Journaled) is only for genuinely old machines. Close Disk Utility afterwards and select Reinstall macOS from the Recovery menu.
Two things are worth knowing in advance. The reinstall downloads macOS across the internet and is not a five-minute affair, so use a connection that will hold up and keep the charger attached throughout. The more important point concerns what the erase actually achieves. Where FileVault was never switched on, erasing an Intel Mac is not destruction. The references to your files are removed and the files themselves stay exactly where they were, waiting to be overwritten, and any competent laboratory will retrieve a substantial amount of them. That is welcome news if the machine you wiped was the wrong one. It is a genuine problem if you have already handed it to a buyer you have never met. The fix is to enable FileVault and let the encryption complete before erasing anything — or to remove the disk altogether and have it destroyed.
Sooner or later the question changes from how do I wipe this to how do I make sure nobody ever reads it — a cupboard of retired drives, a practice clearing closed files, a server that has sat in a storeroom since the last migration. A quick format achieves nothing here at all; the disk walks out of the building as readable as it went in. On a mechanical drive there are exactly two answers that stand up. One is a full overwrite of every addressable sector, which runs for hours per drive and only works if the drive is healthy enough to accept every write. The other is physical destruction of the platters themselves, and the emphasis belongs on platters. Putting a drill through the casing does not qualify: the bit contacts a tiny fraction of the recording area, and everything it misses remains readable to anyone with a bench and some patience.
Solid-state media does not follow those rules, which is where people come unstuck. A controller decides for itself where any given write physically lands, and every SSD and memory card keeps reserve capacity that no command from your side can address, so blocks you are confident you have overwritten may still be sitting intact in that reserve. Three approaches do work: the drive's own hardware secure erase, a cryptographic erase on media that was encrypted from new, or reduction to particles small enough to defeat chip-level reading where the material genuinely warrants it. None of that is offered here — this is a laboratory, not a disposal contractor, and pretending otherwise would not help you. For any quantity, engage a company that shreds to a published standard and hands you a certificate an auditor will accept. The only promise made about devices sent in for recovery is that they go back to you, or are destroyed securely on your written instruction when the work finishes. Nothing is thrown away.
A good proportion of the people who arrive at a page like this are not selling anything to anybody. They have gone looking for a reset because the machine has already stopped working properly — it hangs before the desktop appears, the internal storage has vanished from Disk Utility, or the screen shows a folder with a question mark blinking in the middle of it. A reset addresses none of those. It is in fact the most damaging thing available to you at that moment, because it discards the last remaining copy of your data and leaves the underlying fault completely untouched.
Put it down instead. Plenty of iMacs and MacBooks up to a certain generation take a drive that comes out with a few screws or a clip, and once removed it can be read on a bench irrespective of whether the computer will ever start again. Post it insured and tracked to Guildford Data Recovery, Building 2, Ground Floor, Guildford Business Park, Guildford, GU2 8XH — or drive it down, which takes about forty minutes from Bracknell along the A322 and the A3, and hand it to reception between 9:00am and 5:30pm, Mon–Fri. There is no collection service and no counter in Bracknell, so the whole thing amounts to one parcel and one call on 0800 689 0668. Diagnosis is free and finishes 2 working days after booking in; a single hard drive or SSD is £300 + VAT, confirmed in writing before anything is chargeable.
The one honest no on this page is storage soldered to the logic board, which is how every Apple Silicon machine and a number of ultrabooks are built. There is nothing to unclip and nothing to post, and if the board itself has failed the data goes with it. Better said here than after somebody has charged you to find out.
Copy first, sign out second, erase third. The erase is the only step that takes five minutes and the only one that cannot be redone — everything expensive on this page comes from doing one of the two steps before it out of order, or not at all.
Free diagnostic closing 2 working days after your device is booked in, one fixed written quote, and no fix, no fee on logical faults. Cards and USB sticks £250 + VAT, any single drive or SSD £300 + VAT.