WARNING! Applying a master reset on your device will return it to factory values, thus you will lose all personal data stored on the internal memory, including downloaded apps, content, photos, custom ringtones and contacts. Content stored on the SIM and SD cards will not be deleted.

NOTE: Before applying a master reset, you might want to back up your data. For a full guide, visit this link. To learn how to restore your data after a back up, visit this link instead.

Master Resetting via the Settings Menu:

  1. While on the home screen, tap the "Apps" icon
  2. Tap "Settings"
  3. Under "User and Backup", tap "Backup and reset"
  4. If you wish, clear the check boxes next to "Automatic restore" and "Back up my data"
  5. Tap "Factory data reset" > "Reset device"
  6. Assuming that you have screen lock enabled, enter your password or PIN and tap "Continue"
  7. Tap "Delete all" to confirm

Master Resetting Using Hardware Keys:

NOTE: Use this method of resetting in case you are unable to factory reset your smartphone using the settings menu.

  1. Power off your smartphone
  2. Press and hold the "Volume Up", "Home" and "Power" buttons at the same time
  3. After the phone vibrates once, release the "Power" button but keep pressing "Home" and "Volume Up"
  4. Once the "Android System Recovery" screen appears, release all the hardware buttons
  5. Press "Volume down" until you highlight "wipe data / factory reset"
  6. Press the "Power" button to select the option
  7. Navigate to "Yes -- delete all user data" using the "Volume Down" button
  8. Press "Power" to confirm the master reset
  9. After the device has been reset, the "Reboot system now" option should be highlighted
  10. Finally, press the "Power" button to reboot your device

See More: Samsung Galaxy S5: Master Reset via the Settings Menu and Hardware Buttons