The app offers a coaching function where users receive personalized messages to encourage smoking cessation and advice for behavioural changes. For the first 4 weeks of the intervention, individuals will also be asked to blow daily into a breath carbon monoxide monitor before going to sleep. Depending on the results of the breath test, individualized messages will be delivered by the Smokelyzer feedback app to either enhance maintenance of abstinence or increase the motivation to quit. After the first 4 weeks, participants will use the breath carbon monoxide monitor at least twice a week until the end of the 6-month study. The app will react with positive feedback in individuals doing well with smoking cessation and messages to encourage individuals with difficulties quitting to smoke.

Participants in the control group will be managed according to usual care as regularly provided by their SHCS physicians. Physicians will motivate patients to quit, emphasise the advantage of quitting, and provide patients with an information card that contains short advices how to quit and addresses of stop smoking clinics. The Swiss HIV Cohort Study study nurse will enter past or current use as well as of nicotine replacement therapy or use of other pharmaceutical support to quit smoking in the online study form

Smartphone app and carbon monoxide self-monitoring (personal device)