Go to System > Advanced > Reset Options > Erase All Data (Factory Reset) > Reset Phone. You may need to enter a password or PIN. Finally, tap Erase Everything.

Does a factory reset delete everything?

When you do a factory reset on your Android device, it erases all the data on your device. It is similar to the concept of formatting a computer hard drive, which deletes all the pointers to your data, so the computer no longer knows where the data is stored.

How do you force a factory reset on Android?

Press and hold the power and volume up buttons together to load the recovery mode. Using the Volume buttons to scroll through the menu, highlight Wipe data/factory reset. Press the Power button to select. Highlight and select Yes to confirm the reset.