Giving students opportunities to work collaboratively with complex online information is important for the development of democratic citizenship, but providing and structuring these opportunities poses pedagogical challenges. In this study, we investigate how digital mapping tools developed within Science and Technology Studies (STS) are used by upper secondary science students for the collaborative exploration and ordering of controversial socio-scientific issues (SSIs) found online. Our sociocultural approach to detailed analysis of video data reveals how students synchronously construct shared interactive visualizations and respond collaboratively to mediating features of the network visualization tool for handling multiple perspectives and information encountered online. The analysis shows how the tool-mediated activity provided means for students to work out what is relevant and useful in a corpus of online data. We unpack the details of the complex dynamics of this process of evaluating and categorizing websites, uncovering ways that interaction with emerging knowledge artefacts is co-constitutive of participation in the local setting. In particular, this analysis reveals how the tool-mediating activity slows down the process of judging and categorizing online material in terms of criteria such as institutional status, trustworthiness, and position of a controversy. Furthermore, it reveals that alignments and misalignments between the digital tool used and students' own logics prompted students to engage in productive collaborative negotiation of how to make sense of a controversy.