This method works for 90% of ZKTeco standalone devices (K, F, MB, T models).
: If you are also updating the management software (like Check Time), you must remember to "update database" under the maintenance menu to ensure your existing employee records and schedules remain intact. User Frustrations and "Gotchas" Zkteco Update Firmware
Firmware files are available at no cost via official support channels. This method works for 90% of ZKTeco standalone