We discuss how an asynchronous online forum can be used to support the learning of proof validation. In this study, one face-to-face class session was replaced with an online session in a first-year university introduction to proof course with 19 volunteer research participants. The online session was centered around an online forum that took the form of gallery that contained snapshots of five different purported proofs. The purported proofs could be viewed collectively by swiping back and forth and students could leave comments and heart/like the individual snapshots. The online forum was augmented by providing students with criteria of a "good" purported proof and having students complete and view the results of an online class poll. Here, we discuss how the online session enhanced learning by sharing students' decision about proof validation before and after they participated in the online forum and students' experiences of the online session.