Inclusion criteria:
Adult smoker:
1. 18 years or older
2. Daily smoker (at least one cigarette per day)
3. Intention to quit smoking
4. Own a smartphone with access to mobile internet and daily use
5. Fluent in the German language
Buddies:
1. 18 years or older
2. Current non-smoker (at least 6 months abstinence of tobacco and e-cigarettes)
3. Own a smartphone with access to mobile internet and daily use
4. Fluent in the German language
Exclusion criteria:
Adult smoker:
1. Younger than 18 years old
2. Less than daily smoking
3. 24-hour shift work
4. Simultaneous participation in a professional smoking cessation program or active use of a smoking cessation application
5. Insufficient comprehension of the German language.
Buddies:
1. Current smoker
2. 24-hour shift work
3. Younger than 18 years old
4. Insufficient comprehension of the German language