Design
A two-arm parallel randomized controlled feasibility trial, allocating smokers recruited online (1:1 ratio) to a “usual care” arm (referral to NHS SmokeFree website) or an intervention arm who received “usual care” plus an invitation to install the Quit Sense app. A nested qualitative process evaluation and a Study-Within-A-Trial (SWAT), evaluating retention incentives, were also undertaken though reported elsewhere. For full details of study methods, see the trial protocol.Ethical approval was received by the Wales REC7 NHS Research Ethics Committee (19/WA/0361) and a trial steering committee with a majority of independent members oversaw trial conduct. The trial was preregistered (ISRCTN12326962).