How to erase your data properly before selling a phone

Why a factory reset alone is not enough

Every Android and iPhone sold in the last decade encrypts its storage by default. A factory reset discards the encryption key, which is why the old data is unrecoverable in practice — this part genuinely works.

The problem is not the data. It is the lock. Android's Factory Reset Protection and Apple's Activation Lock both tie the hardware to the account that was signed in when it was reset. Wipe the phone without signing out and you hand over a device that stops at setup and asks for your password.

For a buyback service that is a failed sale. For a private buyer it is a dispute. Either way the fix requires you, which is awkward once the phone is gone.

Step 1 — back up what you are about to destroy

Do this the night before, not on the doorstep. A full backup of a well-used phone moves tens of gigabytes and needs both time and a stable connection.

• Android: Settings › Google › Backup, then confirm the last backup time. Photos need Google Photos backup finished separately — check the sync status, not just the setting.
• iPhone: Settings › [your name] › iCloud › iCloud Backup, then Back Up Now. Or plug into a computer and take a local encrypted backup, which is faster and includes saved passwords.
• WhatsApp: back it up inside the app as well. It is not fully covered by either platform backup.
• Authenticator apps: move your 2FA codes to the new phone before the wipe, or you will lock yourself out of your own accounts.

Step 2 — sign out and release the locks

Step 3 — reset, then check the result

Now run the reset: Settings › System › Reset options › Erase all data on Android, or Settings › General › Transfer or Reset iPhone › Erase All Content and Settings on iPhone.

When it reboots, walk through the first two setup screens yourself. If it asks for a Google account or an Apple ID that is not yours to give, the sign-out did not take and you need to repeat step 2 — which you can only do while the phone is still with you.

What does not need doing

Two pieces of internet advice are worth ignoring. The first is filling the phone with junk files and resetting again to "overwrite" the old data — on an encrypted device this achieves nothing beyond wear. The second is third-party "secure eraser" apps, which cannot reach below the operating system anyway.

What does matter is physical: take out the SIM tray, take out the microSD card if there is one, and check the case pocket if you are selling that too.

If you are selling through a pickup service

Do the wipe anyway, before the rider arrives. A good inspector will offer to reset the phone in front of you, and that is a useful safety net — but a phone that arrives already clean and signed out cannot fail the sale on a lock.

It also shortens the visit. Our own pickups take about ten minutes when the phone is ready, and considerably longer when a backup is still running.