  Background: Hackathons have become popular events for teams to collaborate on
projects and develop software prototypes. Most existing research focuses on
activities during an event with limited attention to the evolution of the code
brought to or created during a hackathon. Aim: We aim to understand the
evolution of hackathon-related code, specifically, how much hackathon teams
rely on pre-existing code or how much new code they develop during a hackathon.
Moreover, we aim to understand if and where that code gets reused. Method: We
collected information about 22,183 hackathon projects from DEVPOST -- a
hackathon database -- and obtained related code (blobs), authors, and project
characteristics from the World of Code. We investigated if code blobs in
hackathon projects were created before, during, or after an event by
identifying the original blob creation date and author, and also checked if the
original author was a hackathon project member. We tracked code reuse by first
identifying all commits containing blobs created during an event before
determining all projects that contain those commits. Result: While only
approximately 9.14% of the code blobs are created during hackathons, this
amount is still significant considering the time and member constraints of such
events. Approximately a third of these code blobs get reused in other projects.
Conclusion: Our study demonstrates to what extent pre-existing code is used and
new code is created during a hackathon and how much of it is reused elsewhere
afterwards. Our findings help to better understand code reuse as a phenomenon
and the role of hackathons in this context and can serve as a starting point
for further studies in this area.
