Detailed app utilization data during the 8-week treatment period for SmartQuit were collected by 2Morrow Inc., the Seattle-based mobile software development company contracted to program the app. At 60-days post-randomization, participants were asked to complete a follow-up survey. Multimodal surveys were employed to maximize data completeness. Participants were first sent an email with a link to complete the follow-up survey online. An additional two reminders were sent by e-mail. For those not responding to the e-mail request, research staff contacted the participant to administer the survey by phone. If the phone contact was not successful, a paper copy of the survey was mailed along with a $2 bill pre-incentive to encourage participation.