Here's how to securely wipe your Android smartphone for resale

Got your eye on a new Android smartphone? Here's how to wipe your existing smartphone so you can sell it or pass it on to a family member or friend without giving them all your data as well.
Written by Adrian Kingsley-Hughes, Senior Contributing Editor

Found a new Android smartphone that you want to buy? Here are the steps you need to go through to safely and securely wipe the data off your existing smartphone before you're done with it.

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  1. Back up all your data; because once it's gone, it's gone. There's no undo button you can press. No "oh… wait…" No undelete.
  2. Next, plug the charger into the device so it's getting power for the deletion process, because it can take a very long time. Or at the very least make sure it's fully charged.
  3. If you are running Android 5.0 "Lollipop" or later, you need to deal with the Android Factory Reset Protection (FRP) feature. This is designed to stop thieves (or pranksters) from wiping your smartphone. First you need to remove the screen lock. The first step on a stock Android install is to go to Settings > Security & Location > Screen Lock and select None. On Samsung Galaxy hardware, you go to Settings > Lock Screen & Security > Screen Lock Type and select None.
  4. Next step is to remove your Google account (or accounts if you have multiple ones installed). On stock Android go to Settings > Accounts > Google and choose Remove Account. On Samsung Galaxy hardware, this is a little different: Settings > Cloud & Accounts > Accounts and then choose Google, then finally select Remove Account.
  5. There's a final step on Samsung Galaxy smartphones, which is to delete the Samsung account. To do this go to Settings > Lock screen & Security > Find My Mobile. From there enter your password, tap on your account, and then choose More > Remove Account.
  6. Go to Settings > Security > Encrypt phone to begin the process. On Samsung Galaxy hardware, go to Settings > Lock Screen & Security > Protect Encrypted Data.
  7. You will be guided through the process. Set a strong password. Don't bother encrypting the SD card because you can pop this out and keep it rather than wipe it. This process can take a long time, so be patient and make sure you have the time.
  8. Finally, it's time to factory reset the hardware. On Stock Android you do this by going to Settings Backup & Reset Factory Data Reset and select Reset Phone.
  9. Once this process is completed, your data is gone. Technically, it's still written there on the flash memory in what is now reported as free space, and will eventually be overwritten. Because it's encrypted, recovering it would be extremely difficult. However, if you want to completely eradicate it, jump to the next step.
  10. The best way to get rid of the encrypted data is to overwrite it with new data. There are two ways you can do this. You can load some big files onto the device (big video files are ideal for this) until the storage is full up and then delete these files, or you can use a custom app such as iShredder to digitally "shred" the data.

That's it! Your data is now gone, and you're safe to pass the smartphone or tablet on.

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