Quitting smoking at any age increases life expectancy, but older adults face barriers to receiving cessation services. Despite the promise of web-based smoking cessation interventions to help address access barriers, whether older adults who participate in smoking cessation programs engage with and benefit from these tools at the same rate as younger adults remains unknown. In this secondary analysis, we compared engagement and satisfaction with two web-based smoking cessation interventions and quit rates between older, middle-aged, and young adults in the United States enrolled in the WebQuit trial between March 2014 and August 2015. Participants were divided into age groups: older (60 years and older, n = 439/2637), middle-aged (40-59 years, n = 1308/2637), and young adults (18-39 years, n = 890/2637). Treatment engagement and satisfaction, and 12-month quit rates (self-reported complete-case 30-day PPA and missing-as-smoking) were compared between groups. Older adults engaged more with the websites than young adults through multiple indicators of intervention engagement (i.e., number of sessions, unique days of use, and time spent on the site), and older adults spent more time on the site per session than their counterparts. Satisfaction with websites was high (81%) and non-differential between groups. Older and middle-aged adults quit smoking at a similar rate as younger adults (24%, 24%, 27%, respectively, p = 0.905). Older and middle-aged adults who participated in a web-delivered smoking cessation intervention engaged more with the intervention than their younger counterparts and they quit smoking at a similar rate, thereby demonstrating high acceptability and potential of digital interventions to help older adults quit smoking. Trial registration:ClinicalTrials.gov Identifier: NCT1166334.