Background Cigarette packs are a form of advertising that distributes brand information wherever smokers go. In the 21st century, tobacco companies began using onserts on cigarette packs to communicate new advertising messages to smokers.

Methods We reviewed tobacco industry documents dated 1926 to 2017 to identify how the tobacco industry developed and used onserts in marketing and to serve the industry’s political and legal objectives.

Results Onserts added to cigarette packs became a more cost-effective way for brands to market in the year 2000. Manufacturers then began studying them, finding that new messages were appealing, while repeated messages were ignored. By 2005, tobacco companies were using onserts to effectively communicate about new tobacco products and packaging changes. They also used repeated ‘corporate responsibility’ messages that were, according to the industry’s own research, likely to be ignored.

Conclusions Tobacco companies have expanded on cigarette pack-based advertising. Twenty-first century onserts simultaneously seek to increase sales using materials that are novel, attractive and provide independent value, while undercutting public health messages about the risks of tobacco use using materials that repeat over time and are comparatively unattractive. Health authorities can use this industry research to mandate onserts to communicate effective health messages.