Updating a smartphone operating system often brings new features and security improvements, but users often encounter performance or application compatibility problems after installing the latest version. If your gadget begins to work unstable, quickly discharges or displays the interface incorrectly after switching to Android 10, the only way out may be to return to the previous version, for example Android 9 Pie. This process, known as downgrading, is a complex procedure that requires care and strict adherence to instructions.
Unlike a regular update, system rollback is not provided for by the standard smartphone settings and requires manual intervention in the bootloader and system memory partitions. You will have to completely erase all data from the device, since the file structure in different OS versions can be radically different. Before you start, make sure you understand the risks: incorrect actions can turn your phone into a “brick” that cannot be restored at home.
This article will analyze in detail all the stages of preparation, searching for the necessary firmware files and the actual process of installing the old version of the system. We will consider methods for different manufacturers, since the Samsung, Xiaomi and Google Pixel procedures may vary significantly. The main rule here is not to rush and double-check every step in order to avoid fatal errors when working with the bootloader.
Risk assessment and device preparation
Before starting any manipulations with system software, you must realize that downgrading is always a risk. Smartphone manufacturers often block the ability to roll back a version to protect user data and system integrity. If you try to install old firmware on a device with a locked bootloader or the wrong version of the boot image, the process may be interrupted in the middle.
The most critical point is complete data loss. When switching from Android 10 to Android 9 the data encryption format may change, making old files unreadable or causing an error during download. Therefore, it is mandatory to create a complete backup copy of all important files, contacts and photos on an external drive or in cloud storage.
⚠️ Attention: If you have a custom recovery installed (for example, TWRP), make sure that it is compatible with the Android version 9. Using an incompatible recovery may lead to an error when installing the firmware.
Also It's worth checking the battery level. The flashing process can take from 15 minutes to an hour, and a sudden power outage at this moment is fatal to the system. Charge the device to at least 80%, and preferably up to 100%, in order to have a reserve of energy in case of freezes or repeated recording attempts.
Use the original USB cable and connect it directly to the port of the computer's motherboard, avoiding the use of USB hubs or front ports of the case, as they can produce unstable voltage.
Searching for and selecting a compatible one firmware
The success of the operation depends 90% on the correctness of the selected firmware file. You can’t just download any image Android 9 from the Internet; it must strictly correspond to your device model, production region and current version of the radio module. Installing incompatible software can lead to loss of connection, non-functioning sensor or constant reboots.
To find the required file, use official developer forums, such as 4PDA or XDA Developers, as well as specialized stock firmware aggregator sites. You need to find out the exact model of the device (for example, SM-G975F) and the region code (CSC), which is often indicated in the phone settings or on the box.
Pay attention to the assembly numbering. Typically, the firmware version for Android 9 should be newer or equal to the version of the bootloader that is already installed on your phone, but older according to the version of the OS itself. If you try to roll back the Bootloader to an older version, Anti-Rollback protection will work and the device will refuse to boot.
- 🔍 Check the exact model of the device in the section
Settings → About phone. - 💾 Make sure that the firmware file has the extension, suitable for your installation method (for example
.zipfor recovery or.tarfor Odin). - 🌐 Check the region code (CSC) of the firmware with the code of your device to avoid problems with localized services.
After downloading the file, be sure to check its checksum (MD5 or SHA-256), if provided by the firmware author. This ensures that the file was not damaged during download and does not contain errors that can only appear during the writing process to flash memory.
Where to look for drivers?
Drivers for your device are usually located on the manufacturer's official website in the support section. For devices on Qualcomm processors, you may need separate ADB and Fastboot drivers, and for Samsung, USB drivers as part of the Odin app.
Unlocking the bootloader and Fastboot mode
Most modern smartphones come with a locked bootloader (Bootloader), which prevents the installation of software not signed by the manufacturer. To downgrade, you will most likely need to unlock it, which is not officially permitted by all vendors.
The unlocking process usually begins with obtaining a special code or permission from the manufacturer. On Xiaomi devices you need to wait several days after linking your account, and on Samsung you just need to activate the item in the developer menu. After receiving permission, the device reboots into the mode Fastboot or Download Mode.
| Manufacturer | Button combination | Unlock features |
|---|---|---|
| Xiaomi / Redmi | Volume down + Power | Requires a wait of 7-15 days and the Mi Unlock utility |
| Samsung | Volume down + Volume up + USB | The Knox counter is triggered, the warranty is void |
| Google Pixel | Volume down + Power | Unlock via command fastboot in the developer menu |
| OnePlus | Volume up + Power | Requires an unlock token request on the website |
Remember that unlocking the bootloader automatically initiates a full data reset (Wipe Data). This is another reason to make a backup in advance. After unlocking, the device becomes vulnerable to malware, so after completing all work, it is recommended to lock it again, if possible.
Installation instructions via Recovery Mode
The most common rollback method is to use the mode recovery (Recovery Mode). This method is suitable for devices with an unlocked bootloader and allows you to install the firmware file located in the internal memory or SD card. The recovery interface can be stock or custom (for example, TWRP).
First, copy the downloaded firmware file Android 9 to the root of the device’s internal memory or to an external card. Then turn off your smartphone and enter recovery mode using a combination of buttons (usually Volume Up + Power). In the recovery menu, the first thing you need to do is clear the data.
Select item Wipe Data / Factory Reset and confirm the action. This will erase all user data and settings, returning the memory partitions to a clean state. Then go to item Install or Apply update from storage, find your firmware file and start the installation.
☑️ Checklist before flashing
The installation process may take several minutes. A progress bar will be displayed on the screen. Under no circumstances should you interrupt the process or manually reboot your device until a success message appears. After that, select the item Reboot System Now.
⚠️ Attention: If after rebooting the phone freezes at the logo (bootloop), do not panic. Try to enter recovery again and perform a full wipe (Format Data), then repeat the firmware installation.
Firmware method via computer (ADB and Fastboot)
For some devices, especially the line Google Pixel and some models Xiaomi, more a reliable way is to flash the firmware through a computer using tools ADB i Fastboot. This method allows you to control each stage of writing partitions and is often used when recovery does not see the firmware file.
You will need to unpack the archive with the firmware on your computer. Inside there are usually scripts for automatic installation (for example flash-all.bat for Windows or flash-all.sh for Linux/Mac). Before starting, make sure that Android USB drivers and Platform-Tools are installed on your PC.
fastboot flash boot boot.imgfastboot flash system system.img
fastboot flash recovery recovery.img
fastboot reboot
If you use the manual method, the commands are entered sequentially for each section. Be extremely careful: command fastboot flash overwrites data without warning. An error in the partition name or file can lead to the inability of a specific phone function, for example, a Wi-Fi module or a camera.
After completing all commands, the device will automatically reboot. The first launch after this procedure may take longer than usual (up to 10 minutes), as the system optimizes applications and creates new cache files. Do not touch the phone at this time.
Using flash-all scripts automates the process, but before starting, open the script file in notepad and check if there is a command to clear the bootloader (flash bootloader) if you do not plan to change it.
Possible problems and solutions
Even with With careful preparation, unforeseen situations may arise. One of the most common problems is the signature verification error (Signature Verification Failed). This means that the recovery refuses to install the firmware, since it is not signed with the official key of the manufacturer.
In this case, only using a custom recovery, such as TWRPwhich allows you to disable signature verification in the settings, will help. It is also possible for an error Downgrade Protectionto appear if the manufacturer has implemented version rollback protection. It is almost impossible to bypass it at home without special equipment (programmer).
If after installation Android 9 the fingerprint or face stops working, this may indicate incompatibility of the security drivers of the new (old) system with the current security module. In this case, a complete flashing of all partitions, including vendor and modem, via a computer often helps.
- 🔋 The phone does not turn on: Try entering the Download/Fastboot mode and flashing the device again.
- 📶 No network: Check the version radio module (Baseband) and, if necessary, update it separately.
- 🔄 Permanent reboot: Perform a full reset (Wipe Data/Cache/Dalvik) in Recovery mode.
If the device has stopped responding to buttons and is not detected by the computer, it may have gone into deep protection mode (Hard Brick). For recovery, you may need to use specialized software like EDL Mode for Qualcomm or SP Flash Tool for MediaTek, which requires certain skills.
What to do if the firmware cannot be installed due to error 7 in TWRP?
Error 7 means incompatibility Android versions. You need to either update the TWRP recovery itself to the latest version, or try to install the firmware via a computer, or look for a modified updater-script file inside the firmware archive and edit it manually.
Can I roll back if I have already received root access?
The presence of root access does not prevent the rollback, but before the procedure it is better to delete the manager superuser (Magisk/SuperSU) and restore the stock boot image (boot.img) to avoid conflicts when installing a clean system.
Will the IMEI be reset after a rollback?
When flashing the stock image correctly, the IMEI is preserved, since it is stored in a protected EFS/Persist partition, which is usually not affected by OS update. However, when manually flashed via Fastboot, there is a risk of overwriting this partition if you select the wrong file.
Will the guarantee remain after downgrade?
In most cases, no. The very fact of unlocking the bootloader and installing unofficial or older software is often recorded by the manufacturer's counters (for example, Knox from Samsung), which automatically voids the warranty.
How to get all the data back after a rollback?
After booting into Android 9, log in to your Google account. The system will offer to restore data from a cloud backup. To restore photos and files, use a previously created copy on a PC or in a cloud service, downloading them manually.