csctool

Change the CSC (region/carrier code) on a Samsung phone without root and without tripping Knox — a command-line equivalent of the "Change CSC" feature in the SamFW tool.

How it works

Samsung firmware is multi-CSC: one bundle ships many region configs in the OMC partitions already on the device. Dialing *#0*# puts the phone in Test Mode, which exposes a USB modem serial port. csctool opens that port and sends Samsung's pre-configurator AT commands to activate a different CSC from the bundle:

AT+SWATD=0            disable the SW anti-theft guard
AT+ACTIVATE=0,0,0     deactivate the current config
AT+SWATD=1            re-enable the guard
AT+PRECONFG=2,<CSC>   activate the target CSC
AT+CFUN=1,1           reboot

The phone reboots into the new region config. Knox stays intact (this is Samsung's own mechanism, bootloader untouched).

Warning — data loss is device-dependent. On many older devices user data survives the switch, but newer firmware often factory-resets on a sales-code change. Check before you run it:

adb shell getprop ro.omc.changetype

If the answer contains DATA_RESET_ON,TRUE, the phone will wipe user data when the CSC changes. Back up first either way.

Limits

• Only CSCs already inside the phone's bundle can be activated. A code from a different bundle (e.g. a US carrier variant) needs a full firmware flash via Odin.
• Newer devices may factory-reset on CSC change (see the warning above).
• Works on Android 9–11 era firmware. Newer One UI security patches may block the AT interface.
• Back up first anyway — you are reconfiguring the device.
• Some carrier features (e.g. a VoLTE profile) may not match your local network after the change.

Requirements

• Linux or macOS
• adb on PATH (Android platform-tools)
• Python 3.8+ with pyserial
• USB debugging enabled on the phone

Install

pipx install .          # from this directory
# or
pip install pyserial && python3 csctool.py <command>

Usage

csctool info            # model, current CSC, firmware, port status
csctool list            # CSCs bundled in this phone's firmware
csctool change INS      # activate CSC INS (prompts + confirmation)
csctool change INS -y   # skip prompts (assumes Test Mode already dialed)
csctool change EGY --port /dev/ttyACM0

The modem port is auto-detected: /dev/ttyACM* / /dev/ttyUSB* on Linux, /dev/cu.usbmodem* on macOS. Use --port to override.

change walks you through it: it asks you to dial *#0*#, waits for the modem port to appear, confirms, then sends the AT sequence.

Serial permissions (Linux)

If you get a permission error on /dev/ttyACM0, add yourself to the port's group (usually dialout) and re-login:

sudo usermod -aG dialout $USER

or run the command with sudo.

Disclaimer

For use on your own device. Changing the CSC reconfigures carrier/region settings; do it at your own risk.

License

MIT — see LICENSE.