The OnePlus 9 series was launched with Android 11 out of the box, and later received updates to Android 12 and even Android 13. However, there may be reasons why you want to downgrade your OnePlus 9 to Android 11. Perhaps you're experiencing issues with the newer version, or you prefer the familiarity of Android 11. Whatever the reason, downgrading your device can be a bit tricky, but it's doable. In this article, we'll walk you through the process.