When you want to give your device to someone else, how do you ensure that your device is wiped clean of all data? Follow these steps. Just be sure that anything stored on the device is backed up to the cloud or elsewhere. Once the reset is performed, all the data on the device is gone forever.

Android:

Access the Settings menu, either by swiping down from the top of the screen and clicking the “gear” icon, or tapping the Settings icon directly. Scroll down to the “Backup and reset” option, and click. Play it safe and ensure the process completes.
Note that this process should work for both phones and tablets alike.

iOS:

To reset an iPhone, iPad, or iPod touch, access the Settings menu, then select General > Reset > Erase All Content and Settings. If you were using the Find My iPhone option, the device will ask your for your iCloud password to turn it off.

Windows 8 or 8.1:

Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. (If you’re using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, click Settings, and then click Change PC settings.) Then select Update and Recovery, then Recovery. Then click Remove Everything and Reinstall Windows. You’ll also have an option to either quickly or thoroughly clean your data; if you’re the paranoid type, select “Thoroughly.”

Windows 10:

Go to the Settings menu, then Update & Security > Recovery > Reset This PC. Make sure you select the option to remove everything, including your personal files. (You probably don’t need to apply the “scorched earth” policy of overwriting the data on the drives, although if you’re actually going to dispose of the PC, it’s not a bad idea.)

Windows Phones:

Swipe to access the Settings Menu, then click “About.” You’ll see an option to reset your phone.

Some devices also provide the option of remotely wiping them, or erasing their data, either using the native OS or a third-party app. But it’s far more reassuring to perform the reset yourself, with the device in front of you.