How to downgrade your Android phone to a previous version | Android Central

How to downgrade your device (the successful attempt)

I suspect this method would allow you to upgrade your device without an issue, but there are actually a few more steps involved when you’re trying to downgrade your device.

First, I had to reboot the phone back to its regular state, revisit Developer options in the Settings app, and enable an option I forgot about: OEM unlocking.

I then rebooted back into ADB by typing adb reboot bootloader in the Command Prompt. Next, I had to install Google’s USB drivers by downloading them, unzipping them, pulling up Windows’ Device Manager, and manually updating the flagged Android device (by right-clicking, selecting “Update driver,” and pointing to the directory where I previously unzipped Google’s USB drivers).

I unplugged my phone and plugged it back in (for good luck, I suppose), and I was able to confirm my system could see it by typing fastboot devices in the command prompt.

I then downloaded Google’s factory image of Android 9 for my device—not the OTA image I previously pulled—and dropped it into the same folder as my ADB tool.

I felt pretty ready at this point. I unlocked my phone’s bootloader by typing fastboot flashing unlock into the command prompt. This prompted my device to issue a scary little warning, which I ignored; I used the volume buttons to select the new “Unlock the bootloader” option and confirmed using the power button.

While my phone’s bootloader unlocked, I unzipped the factory image I previously downloaded directly into my ADB folder, so its contents were swimming among all the other files. (Don’t unzip them to a new folder within your platform-tools folder.)

Finally, I typed flash-all into my Command Prompt and crossed my fingers. And…that failed, too, because it said the image wasn’t compatible with my device. Sigh.

To get around this issue, I decided to try flashing with a different factory image entirely—the very first “crosshatch” image available for my Pixel 3 XL, “9.0.0 (PD1A.180720.030, Sep 2021).“ I deleted the previous image’s contents from my platform-tools folder, unzipped this image’s contents into the folder like before, and ran flash-all again. And it seemed as if things were working, as I was getting a lot more data about the update processing than before:

After about two minutes, the update finished and my device automatically rebooted. With more fingers crossed—I think I was losing circulation by this point—I powered down my Pixel and manually rebooted it into fastboot mode by holding down the power and volume-down buttons.

Finally, I rebooted my device one final time by selecting the “Start” option on the fastboot screen (using the power button, of course). And—Great Scott!—we’ve traveled back to the past. Here’s that Pixel 3 XL now on Android 9 with the old September 2021 security update:

Installing the android sdk platform-tools package

We’ll be using the command-line tool ADB, short for Android Debug Bridge, to downgrade our Google Pixel 3 XL, which means we have to install the Android SDK Platform-Tools package before we can get started doing anything. Click that link, grab the installer for Windows or Mac, and unzip its contents a folder—your pick.

Make sure your phone is fully updated

This one sounds like a strange step, given we’re trying to downgrade our Pixel device, but hear me out. The downgrade won’t work if there are pending Pixel updates. So, to prevent that, pull up Settings > System >

Step 4: boot device to download mode

You will now have to boot your Samsung device to Download Mode. This is because Odin would only be able to recognize and hence interact with your device in Download Mode. So to boot your device to this mode, you may refer to our detailed guide: How to Boot any Samsung Device to Download Mode.