WARNING! When you factory reset your phone, all your personal data stored on the device will be deleted. This includes media files and ringtones, downloads, apps, contacts etc. Also all settings will be restored to factory values, but data stored on the SIM and SD cards won’t be affected.

Before you reset the phone you can check this thread for back up instructions, and this thread for a guide on restoring data.

Factory Reset via Settings:

  1. Launch “Settings
  2. Go to “Cloud and accounts
  3. Tap “Backup and restore
  4. Optionally, enable or disable “Back up my data” and “Restore
  5. Return to “Settings” and access “General management
  6. Tap “Reset” > “Factory data reset
  7. Tap “Reset” again
  8. If your phone is protected by a lock screen, enter your PIN/password and tap “Continue
  9. When ready, tap “Delete all

Factory Reset via Recovery:

NOTE: If your phone crashes, freezes, or prevents you from resetting it using the method above, alternatively you can try resetting the phone from Android Recovery.

  1. Turn the phone Off if necessary
  2. Press and hold ‘Power” “Volume Up” and the “Home”/”Bixby” keys at the same time
  3. At the Android screen, release the buttons and wait for the Android Recovery menu
  4. Once in Recovery, press “Volume down” repeatedly to navigate the menu and highlight “Wipe data/factory reset
  5. Press “Power” to select the highlighted option
  6. Then, highlight “Yes – delete all user data” and press “Power
  7. After the phone resets, highlight “Reboot system now” if needed and press “Power” again to confirm

Reset Network Settings:

NOTE: When you reset network settings, your saved Bluetooth and Wi-Fi connections will be deleted, while data restrictive settings, background sync settings, and network selection mode will be restored to factory values.

  1. Open “Settings
  2. Access “General Management
  3. Tap “Reset” > “Reset network settings
  4. In case your device is protected by a lock screen, enter your PIN/password
  5. Tap “Reset settings

See More: Samsung Galaxy J3 Star: Factory Reset via Settings/Recovery; Reset Network Settings