The traditional practice of transit information provision considers operators as active communicators of information, while transit users are considered as passive, only receiving information. Encouraging reciprocity and active involvement of users by enabling them to share information may increase transit information quality and ridership. Nowadays, active user participation is starting to take shape with the development of new apps with commercial market potential. This study focuses on willingness to share travel information as part of daily routine transit app use. The applied behavioral framework is the Unified Theory of Acceptance and Use of Technology adapted to the context of information sharing. The empirical analysis consists of estimating a structural equation model on a data set including 1,369 people from Innsbruck and Copenhagen as cities differing in size and general social trust. The results show that the most important motivational factors for information sharing are pro-sharing social norms and self-actualization weighted against effort expectancy, which is more closely related to the logistic effort of using the platform than to network familiarity. Trust in the information provided and social network engagement are secondary motivational factors, with perceived information quality and need of communication being less influential. Greater transit use and interest in level-of-service and real-time information are correlated with greater information sharing motivation. Women and generation Z had higher motivation for information sharing as well as people who reside in Denmark, a country with high social trust.