Once you've saved everything you need from your old device, it's time to securely wipe it so you can dispose of it safely. (For more detail, check out this guide to protecting the data on old devices.) Uninstall apps, deregistering them if necessary, and then restore the machine to factory settings. On Windows, head to Settings, then Update & security, then Recovery, and click Get started under the Reset this PC heading. On macOS, you actually need to reboot your machine, hold down Command+R as it restarts, and choose Disk Utility from the menu. Select your main disk drive, click Erase, and choose Mac OS Extended from the Format menu. You can then quit the Disk Utility program, and select the reinstall macOS option. The process is a little easier on Android and iOS. On Android, choose Settings then System then Reset; on iOS, open the Settings app and choose General, then Reset, then Erase All Content and Settings.