The device tensions and closes strapping bands for packaging and suchlike. It has a band channel open longitudinally on one side in the longitudinal direction of the strapping band, a band tensioning device acting in the area of the band channel and a closing device which joins the band ends lying on top of each other in a tensioned state in the band channel. In order to ensure that correct tensioning rate, band tension, welding time, holding time and/or other band closing parameters in each case, the device is provided with a sensor device recording the width of the strapping band and a processing and adjusting unit interacting therewith, with which the band closing parameters are automatically adjusted as a function of the band width.