Downgrade Oneplus 9 To Android 11 -

Go to Settings > System > System Updates > Settings icon (top right) > Turn off "Auto-download over Wi-Fi."

Download the official OOS 11 downgrade ZIP for your region from OnePlus’s servers:

| Region | Build Number | Download Link | |--------|--------------|----------------| | Global (IN/EU/NA) | 11.2.10.10 | [Link placeholder] | | India | 11.2.10.10.IN11DA | [Link placeholder] | | EU | 11.2.10.10.EU | [Link placeholder] | Downgrade Oneplus 9 To Android 11

Verify SHA256 after download.

This is the most important section of this guide. Go to Settings > System > System Updates

Unlike older smartphones, modern devices have a security feature called Anti-Rollback (ARB). This mechanism prevents users from installing an older version of the operating system if the security patch level on the device has passed a certain threshold.

Tap Install Now or Upgrade. The phone will reboot into recovery mode and begin installing Android 11. This mechanism prevents users from installing an older

Do not touch the phone during this process. You will see a progress bar. The screen may flicker – this is normal.