Guides Recovery
Wiping a device properly before you sell it
Deleting files does not remove them. Here is what actually does, on each kind of device.
Why deleting is not erasing
Deleting a file normally removes the reference, not the contents. The data stays on the drive until something else happens to overwrite it, which is exactly what recovery tools exploit - and they are freely available.
Sign out first
Before wiping anything, sign out of the accounts tied to the device and remove it from your account's device list. On phones and Macs this also releases the activation lock, without which the next owner cannot set the device up at all.
Phones and tablets
Modern phones encrypt storage by default, so the factory reset built into the system is genuinely sufficient: it discards the encryption key, which leaves the remaining data unreadable. Sign out of your account first, then reset from the system settings rather than by holding buttons.
Remove the SIM and any memory card. A memory card is usually not encrypted and is not covered by the reset.
Computers with solid-state drives
If the drive is encrypted - BitLocker on Windows, FileVault on macOS - reinstalling the system and discarding the key is effective for the same reason. Where the platform offers a secure erase, that is the intended route.
Repeatedly overwriting an SSD is not the right approach: wear levelling means writes do not land where you expect, and it wears the drive for no benefit.
Computers with mechanical hard drives
Here overwriting does work, because the mapping between address and physical location is direct. A single full-drive overwrite pass is sufficient for any realistic concern.
When the device is broken
If it will not power on, you cannot erase it. Remove the drive and keep it, or destroy it physically. Handing an unwiped drive to a recycler is trusting a process you cannot see.