How to flash Samsung firmware with Odin
Odin is the Windows tool for installing Samsung firmware over USB. This guide walks through the whole process for a Galaxy phone or tablet with official firmware. Read it to the end once before you start.
What you need
- A Windows PC. Odin runs only on Windows.
- Odin. Use a recent version, such as Odin 3.14.4: old versions can fail on current firmware packages.
- Samsung USB drivers for Windows (official download).
- A USB data cable that you know works, ideally the original one, plugged straight into the PC rather than into a hub.
- The battery charged to at least 50%.
- A backup of your data. Flashing with the CSC file erases the device, and a failed flash can end with a reset too.
- The Google account and password used on the device. After a reset, Factory Reset Protection (FRP) asks for them.
- Firmware for your exact model number. Find it with the firmware search or in the list of models.
Check your model and current build
The model number (for example SM-A556B) is in Settings > About phone. The current build is under Software information. You can also dial *#1234# to see the AP, CP and CSC versions.
The firmware must match the model number exactly. For Odin, SM-S918B and SM-S918U are different devices, even though both are sold as Galaxy S23 Ultra.
Enter Download mode
The key combination depends on the device generation. Switch the device off completely, then hold the keys until a warning screen appears.
- Phones without Home and Bixby buttons (most models since 2019): hold Volume Up + Volume Down and connect the USB cable to the PC.
- Phones with a Bixby button (for example Galaxy S8, S9, S10, Note8, Note9): hold Volume Down + Bixby, then press Power or connect the USB cable, depending on the model.
- Older phones with a Home button: hold Volume Down + Home + Power.
Tablets and some models use other combinations. If nothing happens, look up the exact steps for your model number.
On the warning screen, press Volume Up briefly to continue. Do not hold it: on current devices a long press opens Device unlock mode (bootloader unlock), which erases the device.
You are in Download mode when the screen shows "Downloading... Do not turn off target". In Odin, the ID:COM box lights up with a COM port number and the log shows "Added!!".
To leave Download mode without flashing, hold Volume Down + Power until the device restarts.
The firmware files: BL, AP, CP, CSC and HOME_CSC
The firmware ZIP usually contains five .tar.md5 files. Each one goes into the Odin button with the same name.
| File | What it contains | Odin button |
|---|---|---|
BL_... | Bootloader. | BL |
AP_... | Android system, kernel and recovery. The largest file. | AP |
CP_... | Modem (baseband) firmware. Wi-Fi only tablets may not have it. | CP |
CSC_... | Region and carrier settings plus the partition layout. Erases all data. | CSC |
HOME_CSC_... | The same settings without the wipe. Apps and data are kept. | CSC |
Load either CSC or HOME_CSC into the CSC slot, never both.
- Use CSC for a clean install, to change the region (CSC code), to downgrade or to repair a device that does not boot.
- Use HOME_CSC to update the same model and region while keeping your data. Back up anyway: a failed update can still require a reset.
Flash with Odin, step by step
- Extract the downloaded firmware ZIP to a folder on the PC. You get the .tar.md5 files.
- Install the Samsung USB drivers. Close Samsung Smart Switch if it is running: it can take over the connection.
- Extract Odin and run it as administrator.
- Put the device into Download mode and connect it. Check that Odin shows a COM port and "Added!!".
- Click BL, AP, CP and CSC and select the matching files. Odin checks each file first, and with the large AP file it can look frozen for a while. Wait until the file path appears next to the button.
- Leave the Options tab at its defaults (Auto Reboot and F. Reset Time on). Do not tick Re-Partition or Nand Erase, and do not use the Pit tab.
- Click Start. Do not touch the cable or the device until Odin finishes. This takes several minutes.
- When Odin shows PASS!, the device restarts by itself. The first boot after flashing takes longer than usual: let it finish.
Video: flashing with Odin
Downgrade limits: the bootloader binary
A Samsung device refuses firmware with a lower bootloader revision, usually called the binary, than the one already installed. This anti-rollback protection is built into the device, and Odin cannot bypass it.
The binary is the 5th character from the end of the build number. In A185FXXS1AZI4 it is 1. The letter before it (U or S) is not part of the binary. After 9 come letters: A means 10, B means 11 and so on.
- Same binary: the build can be flashed, including an older one. Going back to an older Android version usually needs the full wipe with CSC.
- Higher binary: the build can be flashed, but afterwards you cannot go back to any build with a lower binary.
- Lower binary: blocked. Odin stops with "SW REV CHECK FAIL".
Every build page on SamFirm.Shop has a "Will it work on my device?" check: paste your current build number and it compares the model, binary and CSC with that build before you download.
Common Odin errors and fixes
SW REV CHECK FAIL
The firmware has a lower bootloader binary than the device. This cannot be forced. Download a build with the same or a higher binary.
FRP lock, RMM / KG lock
FRP: the device is protected by the Google account signed in on it, and it refuses files that are not official for this exact model. Flash official firmware for your model number, then sign in with that Google account after the first boot.
RMM or KG (Knox Guard): the device is locked remotely by a carrier, seller or company. Flashing does not remove this lock. Only the party that set it can release it.
FAIL! (Auth), SECURE CHECK FAIL, MD5
The file is for a different model or variant, or the download is damaged. Compare the model number on the device with the firmware, download the files again and use a recent Odin version. Size or MD5 errors while loading a file usually mean an incomplete download.
Stuck at "Added!!" or device not detected
Odin does not show a COM port, or the flash stops at "SetupConnection" or with "Complete(Write) operation failed". This is almost always the connection: try another cable and another USB port directly on the PC, reinstall the Samsung drivers, close Smart Switch and restart Odin as administrator.
Bootloop after flashing
The device restarts again and again or stays on the Samsung logo after a successful flash. Usually the old data does not fit the new system, typically after HOME_CSC or a downgrade. Boot into recovery and choose "Wipe data/factory reset", or flash again with CSC instead of HOME_CSC. Both erase your data.
To open recovery, switch the device off and hold Volume Up + Power. On current models the USB cable must be connected to a PC. On older models also hold Home or Bixby.
Safety
- Flash only official firmware for your exact model. Official Samsung firmware does not trip Knox and does not unlock the bootloader.
- You flash at your own risk. Back up first, keep the device charged and never disconnect it during the flash.
- For a regular update to the latest build, Samsung Smart Switch or the update in Settings is simpler and safer.