If you're selling your iPhone or just want to start over fresh, you may want to factory reset it. Factory resetting your phone will completely wipe the device. All of your personal data, settings, and more will be removed when the reset is complete. If you to preserve have something critical on your iPhone, be sure to back it up before you begin.
Apple recommends using a computer to reset the iPhone. You can use a Mac or a PC for this process. However, the software you use depends on what computer you have.
If you have a Mac running macOS Catalina 10.15, open the Finder application. If you're using macOS Mojave 10.14 or earlier, open iTunes. Windows users can use iTunes as well.
Using an iPhone to USB cable, connect the iPhone to the computer. If the iPhone is locked with a passcode, you may be prompted to confirm it in a popup. If you see this prompt, go ahead and enter the passcode.
iTunes will show a list of connected Apple devices—this includes both iPhones and iPads. Look for the iPhone you connected on the list and select it by clicking the phone icon in the top left corner.
Congratulations! You've factory reset the iPhone.
Ash