The most reliable resource for downgrading your Go to product viewer dialog for this item.
Use if downgrade fails or device is soft-bricked.
If running OxygenOS 12/13:
Local Update APK: Since newer OxygenOS versions (12+) often hide the "Local Upgrade" option, you may need to install the OnePlus Local Update Tool. Step 2: Prepare the Package
Move the file to the root directory of your phone's internal storage (outside all folders). 2. Install the "Local Update" Tool Downgrade Oneplus 9 To Android 11
OnePlus Clone Phone (formerly Switch): Use the OnePlus Clone Phone app to create a local backup of your contacts, logs, and messages.
Downgrade if:
As of 2025, Android 11 is technically outdated. You will miss out on security patches newer than February 2024 (depending on your final build). However, for many, the stability and performance of Android 11 on the OnePlus 9 outweigh the theoretical security risks—especially if you avoid downloading suspicious APKs.