The following command switches the device with serial number <serial_number> to programming mode, where it accepts DFU packages over a serial connection:
nrfutil device mcu-state-set Programming --serial-number <serial_number>
Programming, you can program the device with nrfutil device program. For the full DFU programming workflow, see the device program command page.
The following command switches the device back to application mode, where the application firmware runs:
nrfutil device mcu-state-set Application --serial-number <serial_number>
Tip
Run nrfutil device list --traits nordicDfu to find devices with a DFU trigger interface. If the device does not appear, put it into programming mode by holding the reset button and reconnecting it to the computer.