Participants from the intervention group will receive CBT based smoking cessation. It provides both mandatory information of evidence-based and guideline-based smoking cessation interventions, and optional information about quitting benefits, tips for quitting et al. The app will be available for the participants in the intervention group until 26-week post-quit date follow-up. After this period, the app will automatically stop the data collection, but they can continue to use it if they want. As the participants progressed through the study, smoking cessation related information will be gradually reduced until 12 weeks after quit date, and follow-up messages will be sent at 16, 20 and 26 weeks after quit date. Participants from intervention group can also seek for help at any time by text or WeChat, or make a phone call.

Participants from the control group will only receive information of thanking them for being in the study and reminding them of the time until their free month at the end of follow up. In order to measure the outcomes between two groups, continuous smoking abstinence, point prevalence of abstinence, how many cigarettes per day during the last week if they are still smoking will be checked at week 1, 2, 3, 4, 8, 12, 16, 20 and 26 points after quit date by ePRO software. Biochemically verified continuously abstinence will also be checked if they have reported continuous smoking abstinence at week 26 points after quit date.

Paticipants will receive 12-week app-based smoking cessation intervention with follow-up to 26 weeks.

Participants in this study will be considered to be biologically verified continuously smoking abstinence if they report smoking no more than 5 cigarettes since the quit date and have an expired carbon monoxide concentration of less than 10 ppm (for local participants who will be able to go to the PI affiliated hospital) or a urine cotinine cutoff point of 200 ng/ml (cotinine urine dipsticks will be mailed to each participant's address, and test will be confirmed by video call and by family members) at week 26 (6 months) after quit date. This abstinence has been applied by the Society for Research on Nicotine and Tobacco (SRNT) (Hughes, Keely et al. 2003) and the 'Russell Standard' (West, Hajek et al. 2005).

7-day Point prevalence of smoking abstinence: not even a puff of smoke, for the last seven consecutive days, at 1, 2, 3, 4, 8, 12, 16, 20 and 26 weeks.