After downgrading your OnePlus 9 device to Android 11:
Last tested: OnePlus 9 LE2115_11_C.15 (Android 11) downgraded from LE2115_13_F.75 (Android 13).
to Android 11 (OxygenOS 11) is a common move for enthusiasts . However, this process is high-stakes; it will , so a full external backup is mandatory before you begin. Essential Pre-Flight Checklist
Use this if the local update fails or if your phone is bricked. This method uses the device's low-level EDL (Emergency Download) mode. How to Downgrade OnePlus OxygenOS via MSM Download Tool
| Issue | Probability | Workaround | |-------|-------------|-------------| | Widevine L1 → L3 | 100% | Permanent due to TAMPER flag | | Fingerprint sensor lag | 20% | Re-enroll after 3 reboots | | 5G NSA not connecting | 15% | Flash modem from CPH2179_11_C.15 | | OTA notification spam | 100% | Use NetGuard firewall to block *.oneplus.com | | Google Pay/SafetyNet fails | 100% | Install Magisk + Universal SafetyNet Fix v2.4.0 |
app (it may appear as a "System Update" icon in your app drawer). in the top right corner.
Because the rollback process triggers a mandatory factory reset, securing your data first is critical.
Once on Android 11, apply these to prevent forced updates:
Prepare a computer and a high-quality USB-C data cable (preferably the original red cable). Phase 2: Download the Official Android 11 Rollback Firmware
This process will completely wipe your device. It performs a factory reset that erases all photos, apps, messages, and settings.
Before proceeding, you must understand that downgrading is a clean-slate process.