The “HacKeYthon” is an event with the goal to bring forward the development of the KeY program verification framework, and, at the same time, unite experienced developers, new project members and associates as well as interested students. Participants work in small groups, which are mixed in terms of experience to enable knowledge transfer, on chosen programming projects related to KeY. The idea of the HacKeYthon was originally conceived by me in 2017, and I was the main organizer of the first such event in 2018.