In this paper, we explore the role technology plays in online workplace harassment as it emerges in the legal verdicts of labour law courts. Analysing 106 official legal verdicts on labour law violations, we demonstrate how technological traces are used as evidence for both indictment and the defence. We find that chat technologies risk providing a platform for online workplace harassment which extends beyond the boundaries of work and into private life. In contrast to online harassment on social media sites, online harassment in the workplace exists within situations of known audiences in hierarchical organisational structures. Thus, speaking up against a violator can have severe financial and social consequences for the survivor. Our data show that chat technology, by capturing and documenting abusive behaviours, makes harassment visible, allowing survivors to hold the harassers legally accountable. Furthermore, we find that online harassment, because it extends beyond the physical workplace, extends the legal and ethical responsibility of the employer. We argue that research on computer-supported co-operative work should consider how the design of co-operative technologies can help survivors speak up, as well as inhibit violators’ abusive behaviour. We also propose that design strategies must consider employers’ extended responsibility for moral and ethical conduct.