Modern smartphones Samsung regularly receive software updates that are designed to improve performance and security. However, in practice, it often happens that after updating One UI the device begins to work unstable, discharges faster or loses its usual interface response speed. In such situations, the only correct solution is to roll back to a previous, more stable version of the operating system.
The procedure of returning to the old firmware on devices of the South Korean giant is technically possible, but requires some preparation and accuracy from the user. You will have to download a specific system image file, put the phone into a special operating mode and use a computer with the firmware software installed. Ignoring security rules at any stage can lead to your Galaxy turn into a “brick.”
In this guide we will analyze in detail all the nuances of the procedure, from finding the required file to the final setup of the device after a successful rollback. We will look at working with the official utility Odin, which is the de facto standard for servicing smartphones of this brand. Follow each step carefully to minimize the risk of data loss.
Device preparation and backup
Before you begin any manipulations with the system memory partition, it is critically important to save all personal data. The procedure for rolling back firmware (Downgrade) on smartphones Samsung implies complete formatting of the user partition. This means that all photos, contacts, messages and installed applications will be permanently deleted.
Use cloud services or connect the device to a computer to create a full copy. Pay special attention to folders with multimedia and files in the internal memory that are not automatically synchronized with your account Google or Samsung Cloud. Make sure that the battery is charged at least 60-70%, since the firmware process is energy-consuming and power interruption is unacceptable.
⚠️ Attention: The system rollback process irreversibly deletes all user data. Creating a backup copy is a mandatory step, neglect of which will lead to loss of information.
You also need to check the model of your device. Go to Settings → About phone and write down the exact alphanumeric model designation (for example, SM-S918B). Firmware from another model, even a very similar one, can permanently disable the phone. Compatibility of software versions also plays a role: usually you can roll back to only one version lower than the one currently installed.
☑️ Preparing for a firmware rollback
Searching and downloading the correct firmware version
The most difficult step is finding the correct firmware file. Official website Samsung does not provide a direct opportunity to download older versions of the software for ordinary users. You will have to use third party firmware databases such as SamMobile, SamFw or Updato. These resources aggregate official dumps released by the manufacturer for different regions.
When selecting a file, pay attention to the Binary (or Bit) column in the version information. This is a technical parameter that prevents an older version from being installed over a new one if the binary number is lower than the current one. If you try to install firmware with a lower binary number through the standard update menu, the system will refuse installation. However, when using the download mode and utility Odin this prohibition can sometimes be bypassed, but only if the difference in versions is not too great.
Make sure that the firmware region (CSC) matches the region of your device or is compatible. Installing firmware from another region may block some functions, such as Wi-Fi Calling or the operation of banking applications in your country.
How to find the current version of the binary (Binary/Bit)?
Go to Settings → About phone → Software information. Look at the "Kernel Version" or "Build Number" line. At the end of the line there is usually a number after the letter (for example, G991BXXS5AUC1, where 5 is the binary number). You cannot install firmware for which this figure is less than the current one.
The downloaded file is usually a .zip or .rar archive. After downloading, you need to unzip it on your computer. Inside you will find several files with .tar or .tar.md5 extensions. It is these files that we will need at the next stage to load into the firmware app.
Installing drivers and preparing the Odin utility
To connect a computer and a smartphone in a special mode, the correct drivers are required. The Windows 10 or 11 operating system often installs them automatically, but for stable operation of the firmware it is better to install the package Samsung USB Driver manually. It can be found on the official developer portal Samsung.
Utility Odin is an internal tool of service centers, which over time became available to the public. Download only verified versions of the app (versions 3.14.x are considered current). After unpacking the archive with the app, run the file Odin3.exe as administrator. This will provide the necessary access rights to USB ports.
The app interface may seem complicated due to the abundance of buttons and fields, but for a basic system rollback we need only a few of them. The main field is the area for downloading firmware files. Modern versions Odin support automatic distribution of files into slots if you use a special CSC file, but manual placement gives more control.
| Slot in Odin | Firmware file (prefix) | Purpose |
|---|---|---|
| BL | BL_... | Bootloader |
| AP | AP_... | Main system and kernel |
| CP | CP_... | Modem and radio communications |
| CSC | CSC_... | Regional settings and reset |
It is important to distinguish between CSC files. There is a file starting with CSC_and a file starting with HOME_CSC_. To perform a full system rollback and reset all settings, you must use the file CSC_. Using HOME_CSC_ will try to save the user data, which when rolling back the version often leads to errors and cyclic reboots.
If the Odin app does not see the phone, try replacing the USB cable with the original one or switching the device to another USB port, preferably directly to the motherboard, and not to the front panel of the case.
Entering boot mode (Download Mode)
In order for the computer to write a new system into the phone’s memory, the device must be in a special service mode, which on devices Samsung is called Download Mode or download mode. The method for entering this mode varies depending on the presence of a physical Home button and the version of Android.
For modern models without a Home button (series Galaxy S20, S21, S22, S23 and later) the procedure is as follows: turn off the smartphone completely. Then press the volume up (Volume Up) and volume down (Volume Down) buttons simultaneously. Without releasing them, connect the USB cable that is already inserted into the computer. A warning will appear on the screen.
For models with a Home button (older series Galaxy S, Note, A), the algorithm is different: turn off the phone, hold down the Home, Volume Down and Power buttons at the same time. When the warning screen appears, release the buttons. In both cases, to confirm the entry, you need to press the volume up button (Volume Up) when the corresponding prompt appears on the screen.
⚠️ Attention: Do not disconnect the USB cable until the firmware process is 100% complete and the phone reboots on its own. Forced shutdown may damage the bootloader.
After successfully entering the mode, you will see a screen with a turquoise background and a warning triangle. At the top of the screen there will be an inscription "Downloading...". It is in this state that the phone is ready to receive data from the utility Odin. If the screen goes dark, simply repeat the login procedure.
The firmware process via Odin
When the phone is in download mode and the drivers are installed, the app Odin should respond. A message <ID:0/00X> Added!!will appear in the app log (upper left window), and one of the ports on the left side of the interface will be highlighted in blue or yellow. This is a signal that the connection has been established and you can start working with files.
Press the buttons corresponding to the slots and select the unpacked firmware files. Sequence of actions:
- 📂 Click BL and select the file starting with
BL_. - 📂 Click AP and select the largest file starting with
AP_. This file may take some time to process. - 📂 Click CP and select the file starting with
CP_. - 📂 Click CSC and select the file starting with
CSC_(not HOME_CSC).
After downloading all files, go to the Optionstab. Make sure that the checkboxes are only opposite Auto Reboot and F. Reset Time. It is strictly forbidden to touch other parameters, such as Re-Partition, unless you use a special PIT file, which is beyond the scope of these instructions.
Press the big button Start. The process of checking checksums and recording data will begin. The log window will display progress as a colored bar. A green bar means success, a red bar means an error. The whole process can take from 5 to 15 minutes depending on the speed of the USB port and the volume of the firmware.
Successful completion of the firmware will be indicated by the appearance of the inscription PASS! in the green square at the top of the Odin window and automatically reboot the smartphone.
First launch and setup after a rollback
After the process is completed, the phone will reboot. The first startup after a system rollback (Factory Reset) can last much longer than usual - up to 10-15 minutes. A logo Samsung or a loading animation may be displayed on the screen. Do not attempt to interrupt this process or remove the battery (if it is non-removable), let the system initialize.
You will see a welcome screen asking you to select a language and connect to Wi-Fi. This is standard procedure for setting up a new device. Since we used the file CSC_, the phone will be absolutely clean, just like immediately after purchase in the store. Restore data from a previously created backup using your account Google or Samsung Cloud.
Check the operation of the main functions: calls, Internet, camera and sensors. Make sure that the software version in the settings matches the one you rolled back to. If the phone works stably, the problem was in the previous update, and returning to the old version was the right solution.
⚠️ Attention: After a system rollback, the automatic update function may again prompt you to install a new version of the software. If you want to stay on the current version, disable automatic updates in the settings or ignore notifications.
In some cases, you may need to clear the cache of the Recovery partition if there are small glitches in the interface. To do this, turn off the phone, hold down the power and volume buttons (the combination depends on the model) to enter the Recovery menu and select Wipe Cache Partition. It is safe and does not delete personal data.
Possible problems and ways to solve them
The process does not always go smoothly. The most common error in the app Odin is FAIL! in the log. There may be several reasons: a bad USB cable, an unstable port, incorrectly selected firmware or driver failure. Try reconnecting the cable, using another USB 2.0 port (black connectors are often more stable than blue USB 3.0 connectors when flashing) and restarting the procedure.
If the phone is stuck on the logo after flashing the firmware (Bootloop), try performing a forced reboot (hold Volume down + Power for 10 seconds) and enter boot mode again. Sometimes re-flashing with the same file helps. In extreme cases, flashing the PIT file may be required, but this is a risky operation that is best left to the service center specialists.
The message “Custom Binary Blocked by FRP Lock” or “RMM State” may also appear. This means that the protection against unauthorized access has been activated or the phone requires an Internet connection to verify your Google account after the reset. In the case of official firmware, this is rare, but if you downloaded the file from an unreliable source, such blocking is possible.
What should I do if Odin hangs at the NAND Write Start stage?
This means that the memory writing process is blocked. Try closing Odin, removing the battery (if possible) or doing a forced reboot using the buttons. Then re-enter Download Mode and try to flash only the AP file, excluding the rest, or use another version of Odin.
Frequently asked questions (FAQ)
Is it possible to roll back Android to any previous version?
No, there is a limit on the binary number (Binary/Bit). You cannot install firmware whose binary number is lower than the currently installed version, even through Odin. Usually, a rollback to only one version back is available.
Will my warranty be removed after rolling back the firmware?
Rolling back to the official firmware using Odin usually does not affect the warranty, since the Knox counter does not increase (remains 0x0). The warranty is only void if you try to install custom firmware, obtain root access or unlock the bootloader.
Is it safe to use the Odin app?
Yes, Odin is an official tool of Samsung service centers. However, you need to download it only from trusted sources to avoid modified versions with malicious code. If you strictly follow the instructions, the risk is minimal.
What to do if the phone says “Secure Check Fail: RMM”?
This is a protection state (RMM State) that blocks the firmware of unofficial images. For official firmware this is rarely a problem. If an error occurs, make sure that you have downloaded the correct regional firmware and that the phone is connected to the Internet to check the status.
Is it possible to roll back the system without a computer?
No, to fully roll back the Android version (downgrade) on Samsung devices, you definitely need a computer with the Odin utility. Through the menu of the phone itself, you can only update to a new version, but not roll back.