How to Downgrade OnePlus 9 from Android 12/13 to Android 11 Downgrading your OnePlus 9 to Android 11 (OxygenOS 11) rolls back unwanted interface changes, restores classic software features, and resolves persistent battery drain or performance bugs introduced in later updates.
Install the OnePlus ROM Upgrade APK file on your device. Execute the Rollback: Open the newly installed app. Select the .zip rollback file you transferred earlier. Click on Install or Confirm . Once complete, the phone will prompt you to restart. Reboot: Click Reboot to start the rollback process. Phase 3: Completing the Downgrade Downgrade Oneplus 9 To Android 11
Choose the method that best suits your technical comfort level. How to Downgrade OnePlus 9 from Android 12/13