Updating the operating system is often perceived as a benefit, bringing new features and security improvements. However, in practice, smartphone owners often encounter the fact that after installing the latest version Android the device begins to work slower, discharge faster, or generate critical errors. This problem is especially acute for models released several years ago, where hardware resources are already at their limit for new software.
In such situations, the only reasonable option is to return to a previous, more stable version of the system. This process is technically complex and carries certain risks, so it requires careful preparation. In this material, we will look in detail at how to roll back Android 10 back to Android 9, using official and alternative recovery methods.
You should immediately understand that downgrading is not just installing an old application. This is a complete flashing of the system partition, which almost always entails complete loss of user data. Ignoring this fact may result in you losing contacts, photos and important documents beyond recovery.
Risk assessment and device preparation
Before you begin any manipulations with the system software, you need to understand the degree of responsibility. Smartphone manufacturers generally discourage downgrading to older versions, as this may create security vulnerabilities or cause the device to become unstable. In some cases, trying to install old firmware can lead to the gadget becoming bricked, when it stops turning on altogether.
The key step is to create a full backup copy. Standard cloud synchronization tools may not preserve all data, especially if the file structure has changed between OS versions. It is recommended to use local copying to a computer or external drive.
⚠️ Attention: The downgrade process will void the device warranty in most service centers. If your smartphone is still under warranty, it is better to contact the manufacturer's official support before starting work.
It is also critical to check the battery charge level. Interruption of the firmware process due to battery discharge is the most common cause of fatal failures. The device must be charged at least 80%, and it is better to connect it to a power source throughout the entire operation, if the bootloader mode allows it.
- 📁 Make a complete copy of all personal data on a PC or to a cloud storage with double check of file integrity.
- 🔋 Make sure that the battery charge is at least 80% and use the original cable for connections.
- 💻 Install the latest drivers
ADBandFastbooton your computer to correctly recognize the device.
Do not forget that different manufacturers use different bootloader locking methods. Brands like Xiaomi or Huawei may require you to receive a special unlock code, which sometimes takes several days. Without an unlocked bootloader (Unlocked Bootloader), installing a custom recovery or old firmware will be impossible.
Searching and checking firmware compatibility
The success of the operation is 90% dependent on the correct choice of system image. You can’t just download the first file you come across from the forums. The firmware must strictly correspond to the model of your device, including the regional version and hardware revision. Installing firmware from a different model or region may lead to loss of connection (IMEI), inoperability of cameras or complete system failure.
Only verified resources should be the source of official images. For many devices, these are official developer forums, such as XDA Developers, or specialized firmware databases like Sammobile (for Samsung) or MiFlash (for Xiaomi). Look for files marked Stable and version Android 9 Pie.
Pay special attention to the build number. It often happens that between the release of Android 9 and 10, interim security updates were released. It is advisable to look for the version of Android 9 that was the latest before upgrading to 10, or the one from which you previously switched. This minimizes driver conflicts.
Use utilities like CPU-Z or AIDA64 on your smartphone before starting work to accurately record the processor model, kernel version and current build number. This will help you find an exact copy of the old firmware.
After downloading the file, be sure to check its checksum (MD5 or SHA-1). Firmware files are large, and when loading, a recording error may occur, which is invisible to the eye, but fatal to the system. Comparing the hash sums of the downloaded file with the one specified on the source site guarantees the integrity of the data.
| Parameter | Value for Android 9 | Value for Android 10 | Importance of verification |
|---|---|---|---|
| API Level | 28 | 29 | High |
| System partition size | ~2.5 - 3.5 GB | ~3.0 - 4.0 GB | Medium |
| Required Bootloader | Version X or lower | Version Y or higher | Critical |
| Data format | Ext4 | Ext4 / F2FS | High |
Pay attention to the requirements for the bootloader version. In some cases, a new version of Android also updates the bootloader. If you try to roll back the system without first rolling back the bootloader (if possible), the installation process will abort with a signature verification error. Study the documentation for your specific model to find out whether it supports downgrading the bootloader.
Unlocking the bootloader and entering Fastboot mode
The standard phone operating mode is not suitable for performing low-level operations on writing memory partitions. It is necessary to put the device into a special diagnostic and firmware mode. On most devices, this is Fastboot (for Qualcomm processors) or Download Mode (for Exynos).
The login process may vary depending on the manufacturer. Usually you need to turn off your smartphone and then hold down the combination of the volume and power buttons. For example, on many devices this is the volume down button plus the power button. Hold them until the bootloader logo or an image of an Android robot with an open hatch appears.
adb reboot bootloaderThis command, entered into the computer console with the phone connected, will automatically reboot the device into the desired mode if USB debugging was enabled in advance. After entering bootloader mode, connect your phone to your PC with a high-quality cable. The computer must detect the device. You can check this with the command:
fastboot devicesIf you see the device serial number in response, then the connection is established. If the list is empty, the problem is with the drivers or cable. At this point you also need to unlock the bootloader if it is still locked. The command fastboot flashing unlock or fastboot oem unlock will start the reset process.
⚠️ Attention: The bootloader unlock command initiates a full data reset (Wipe Data) automatically. Make sure you have already made a backup, as once you enter this command there will be no way back without losing data.
A warning will appear on the phone screen indicating that the device will be cleaned. Confirm the action with the volume buttons. After the reboot, you will receive a device with an unlocked bootloader, ready to accept unsigned system images.
☑️ Ready for firmware
Installing custom recovery (TWRP)
Standard recovery menu (Stock Recovery) has limited functionality and often prohibits the installation of older firmware versions due to signature verification. To bypass these restrictions, it is recommended to install a custom recovery, the most popular of which is TWRP (Team Win Recovery Project).
Download an image twrp.imgdesigned specifically for your device model. Don't use generic versions. Installation is carried out through a computer in Fastboot mode using the command:
fastboot flash recovery twrp.imgImportant nuance: after flashes of the image, you cannot immediately reboot the phone into the system in the usual way, otherwise the standard recovery will overwrite TWRP. You must immediately hold down the combination of buttons to enter recovery mode (usually Volume Up + Power) to boot directly into the installed TWRP.
In the TWRP menu, first of all, make a full backup of the current system (Nandroid Backup). This will create an exact copy of all partitions to your internal memory or SD card. If something goes wrong during the rollback, you can restore from this save point in a few minutes, returning the phone to the “before all manipulations” state.
What to do if TWRP does not start?
If after installation the screen goes blank or the phone goes into a cyclic reboot, the image may not be suitable or is encrypted. Try finding the TWRP version for your specific Android version or use EDL mode to recover.
Also in the TWRP settings it is worth disabling signature verification (Disable Verity) and forced encryption (Force Encrypt), if such options are available. This will prevent conflicts when installing old firmware, which may use other data encryption algorithms.
The process of rollback via Fastboot and wiping partitions
The most reliable way to rollback is to use Fastboot mode with a full set of system images. This method requires unpacked firmware, where each partition (boot, system, vendor, recovery, etc.) is represented by a separate file .img.
Before writing new images, you must clear old data to avoid file system conflicts. In TWRP mode, go to the Wipe section and select Advanced Wipe. Mark sections Dalvik / ART Cache, Cache, System and Data. Do not select Internal Storage if there are firmware files or backup copies there.
Next follows the firmware process. If you have a script flash_all.bat (for Windows) or flash_all.sh (for Linux/Mac) from the archive with the firmware, the easiest way is to run it. However, downgrading to a version below often requires manual flashing of key partitions with a clear flag.
fastboot flash boot boot.imgfastboot flash system system.img
fastboot flash vendor vendor.img
fastboot flash recovery recovery.img
fastboot reboot
The formatting of the data partition is critical. When moving from Android 10 to 9, the encryption scheme may change. If you simply clear the data, the phone may not boot and require a password that you did not enter. It is recommended to run the command:
fastboot erase userdataOr through TWRP select Format Data (not just Wipe, namely Format), entering the word yes to confirm. This will delete all files, but guarantees a clean file system for the old version of the OS.
The main rule of downgrading: always perform a complete wipe of the Data (Format Data) partition when upgrading to a major version of Android below to avoid encryption errors and cyclic reboots.
After the firmware of all partitions is completed, the device will reboot. The first launch may take from 5 to 15 minutes. Don't panic if you see the manufacturer's logo for longer than usual - the system optimizes applications and creates new caches.
Possible errors and methods for eliminating them
Even if you strictly follow the instructions, unforeseen situations may arise. One of the common problems is the error Downgrade Check Failed or Remote: Device not allowed to flash this image. This means that the bootloader has version rollback protection (Anti-Rollback Protection).
If you encounter such an error, rolling back using official methods becomes impossible without removing this protection, which is impossible programmatically on many modern devices. In this case, the only option is to search for modified bootloaders or wait for a security update, which sometimes resets the version flag.
Another common problem is the “bootlap” (cyclic reboot). If the phone constantly reboots at the logo, try going into TWRP and doing it Wipe Dalvik/ART Cache again. Also check if the partition is properly flashed Vendoras driver incompatibility often causes this failure.
- 🔄 Loading error: try flashing only the partition
boot.imgandrecovery.imgagain. - 📶 No network after rollback: possible incompatibility of the radio module, try flashing the partition
modemorradiofrom the old firmware. - 🔒 Password request: if the system asks for a Google account password (FRP), log in only to the account that was synchronized until reset.
⚠️ Attention: The Recovery and Fastboot menu interfaces may differ depending on the manufacturer and software version. If the commands do not work, check the documentation for your specific model on the relevant forum.
If the device completely fails to respond to commands (black screen, no vibration), you may need to enter emergency recovery mode EDL (Emergency Download Mode) for Qualcomm processors or a similar mode for MediaTek. This allows you to flash a phone even with a “dead” bootloader, but requires an authorized account or special paid tools.
Frequently asked questions (FAQ)
Is it possible to roll back Android without losing data?
Highly not recommended and technically almost impossible when changing a major version (from 10 to 9). The structure of databases and system files changes, which will lead to unstable operation or errors. A full reset (Wipe Data) is required for system stability.
Is it safe to install custom TWRP recovery?
Using TWRP itself is safe if the image is downloaded from the official website of the project. The risk only arises when installing the wrong firmware files through it. TWRP provides a convenient interface for backup and recovery, which reduces the overall risks of the procedure.
What to do if the phone says “Device locked” when flashing the firmware?
This means that the bootloader is locked. You need to run the command fastboot oem unlock or fastboot flashing unlock. Please note that this action will delete all data from your phone. Some brands (Huawei, Xiaomi) require additional unlock codes.
Will the warranty return after a rollback to the factory firmware?
Formally, if you lock the bootloader back and install the official firmware, there may be no traces of intervention left. However, service centers have tools to check the Knox flag (Samsung) or similar trigger counters, which are irreversibly changed when unlocked.
Why does the battery drain even faster after a rollback?
The application optimization process may not be completed yet (this takes up to 24 hours). Also, an older firmware version may not correctly manage the power consumption of a new core or modem. Try resetting the network settings and deleting the Google system services cache.