The present study analyses the use of feedback – a factor that does not necessarily go along with higher performance – when working with fractions via a digital learning platform, and its impact on students' performance. In this context, in 2021/2022 a laboratory study was conducted with seventh graders from German schools. The students were randomly assigned to one out of two experimental groups. Within the groups, all students worked on fraction tasks by using a digital learning platform. The groups differed in the complexity of the feedback (right/wrong feedback vs.
elaborated feedback) presented by the learning platform. Results highlight a low utilisation of right/wrong feedback and a very heterogeneous use of elaborated feedback, with increased use being associated with lower fractions performance. This can be partly explained by the students' prior knowledge. Educational stakeholders should therefore consider how feedback should be designed and implemented in the classroom so that it is (1) used by learners and (2) supports their learning.