WARNING! Factory resetting your phone will result in the deletion of all personal data stored on the internal memory. This includes downloaded content, contacts, media files, applications and so on. Furthermore, all settings will be restored to factory values.

NOTE: To back up your data before resetting the phone, you can visit this thread for instructions.

Factory Reset via Settings:

  1. Tap “Apps” on the home screen
  2. Open “Settings”
  3. Tap “Backup & reset” > “Factory data reset”
  4. At the “Warning” message, tap “Reset phone”
  5. If the phone is protected by a lock screen, enter the PIN / password to proceed
  6. Tap “Continue” > “Erase everything”
  7. Wait for your phone to reset and reboot

Factory Reset via Recovery:

NOTE: In case you are unable to reset the phone using the method above, you can try resetting it from the recovery menu, which can be accessed by performing a combination of button presses.

  1. First, turn off the phone
  2. Next, press and hold “Power” and “Volume Up” at the same time
  3. When an Android appears on the screen, release the buttons
  4. In the “Android system recovery” menu, press “Volume down” to navigate to and highlight “Wipe data / factory reset”
  5. Pressing “Power” will select the highlighted option
  6. Use “Volume Down” to highlight “Yes – delete all user data”
  7. Press “Power” to confirm
  8. After the phone resets, “Reboot system now” will be highlighted
  9. Press “Power” and your device will reboot

Check for OS Updates:

NOTE: After you factory reset your phone, it’s recommended that you check if new software updates are available for your device. To do this:

  1. Tap “Apps” on the home screen
  2. Open “Settings”
  3. Swipe down to “System” and tap “About phone”
  4. Tap “System update”
  5. In case an update is available, follow the on-screen steps to download and install it

See More: ZTE Grand X 3: Factory Reset and Check for OS Updates