Before beginning, ensure you meet these requirements to avoid bricking your device:

To downgrade your to Android 11 (OxygenOS 11), you must use a specific rollback package. This process will erase all data on your device , so a full backup is essential before starting. Critical Pre-Downgrade Checklist Backup Data

Before we dive into the process, it's essential to understand why someone might want to downgrade their OnePlus 9 to Android 11:

, which is a specialized utility for unbricking and deep downgrades via a Windows PC. This requires a computer and puts the phone into "EDL mode" by holding both volume buttons while connecting it via USB. Oneplus 9 Pro | Downgrade to OXYGEN OS 11