9 To Android 11 Exclusive — Downgrade Oneplus

This tool allows you to flash the package. Backup Data: Move all important files to a computer. Step-by-Step: Downgrade OnePlus 9 to Android 11

Before you touch a single file, understand these three non-negotiables:

Tap . Your phone will restart, perform a factory reset, and boot into OxygenOS 11. downgrade oneplus 9 to android 11 exclusive

OnePlus uses specific rollback firmware packages that instruct the system to overwrite the newer OS with the older one.

Ensure the file extension ends strictly in .zip . If it ends in .jar , rename the file and delete the .jar suffix. Step 2: Access the Local Upgrade Menu This tool allows you to flash the package

(via ADB):

The simplest and safest method for downgrading is using an official OnePlus rollback package. These are signed ZIP files that allow you to revert from Android 12 to a specific Android 11 build using the phone’s built‑in System Updater. Your phone will restart, perform a factory reset,

Download and install the official . Grant the app storage permissions when prompted. Step 3: Flash the Android 11 Rollback Package

This disables the system update service entirely.

Move the rollback ZIP to the of your phone's internal storage (not inside any folder). Install the downloaded Local Update APK. Initiate the Rollback : Open the Local Update app you just installed. Tap the gear icon in the top-right corner. Select the Android 11 rollback ZIP package.