Abstract Background Digitalization has significantly expanded the possibilities for collecting health data. Besides options such as online surveys, data can be collected through the use of digital applications (apps). Once users have given their consent, contact information from the app registration can be accessed to invite the relevant target group for further surveys. To generate a sufficient amount of data, a high level of willingness to participate and long-term involvement are required. This study aims to illustrate the willingness to share data and what can be expected from it by means of the Neo-MILK app, which supports mothers during lactation. Methods The willingness to share data and the data resulting from the use of the app is shown by the frequency of consent to the different data use options and the users’ participation. Results While over 68% of the n = 1079 registered app users consented to the use of their app data, 47% agreed to be contacted again for scientific purposes. Data from n = 421 active users were available for analysis. From n = 220 mothers, milk pumping data was available. In 36% of cases, little (<10) or no information on pumping was provided. Of the users who agreed to be contacted again for scientific purposes, n = 300 were invited to participate in another survey and 23% (n = 69) participated. Conclusions In this example, the general willingness to share data and participate in further studies shows great potential for data collection. However, the data collection methods differ primarily in the motivation to participate. When collecting data through app usage, ensuring that the design of the app meets the needs of the user is essential to optimize the user experience and thereby generating complete data. If the use of contact information has been agreed to, incentives may be considered to increase the willingness to participate. Required ethics approvals and data protection regulations should also be ensured for app-based data collection. Key messages • Generating data via app usage as well as the collection of data through the use of users’ contact information shows great potential for health research. • App-based data collection should be considered when planning future health research projects.