Searching constantly for how to factory reset an iPhone? It is always best to do a factory reset iPhone when your device is glitchy, locked, or when you are about to sell it. The process erases all your personal data and settings, restoring your phone to its original, fresh state. You can accomplish this by going to Settings, then transfer or reset iPhone, Erase all content and settings, where you enter your passcode and Apple ID. Remember, it is necessary to save valuable data beforehand, as all the data will be lost.