QR-codes as a tool to increase physical activity level among school children during class hours Introduction: Danish students are no longer fulfilling recommendations for everyday physical activity. Since August 2014, Danish students in public schools are therefore required to be physically active for 45 minutes a day during school hours. An experiment implementing QR-codes as a method to increase physical activity during school hours has been tried. The purpose of this study was to examine if the use of QR-codes as a tool for teaching older classes in Danish public schools could increase the students physical activity level during class hours. Methods: A before-after study was used to examine 12 students physical activity level, measured with pedometers for six lessons. Three lessons of traditional teaching and three lessons, where QR-codes were used to make orienteering in school area. The students motivation for using QR-codes was examined through focus group-interviews and 7 boys and 4 girls completed interview. Results: The students were significantly more physical active in classes, when QR-codes were used as a tool for teaching. The median of student physical activity was 435 steps per lesson in traditionally teaching and 1994 steps per lesson when QR-codes were used. The students generally had positive experiences with the use of QR-codes. In general, the students experienced teaching as more contemporary and exiting than traditional teaching when using QR-codes, which was experienced as old fashioned. The students also felt positive about being physically active in teaching. Discussion and conclusion: QR-codes as a tool for teaching are usable for making students more physically active in teaching. The students were exited for using QR-codes and they experienced a good motivation in teaching.