PurposeComplex social interactions such as argumentation and persuasion are increasingly common in online communications. To better understand these interactions and their impacts on people and on the society, it is important for the authors to understand how people reason online such as when they need to justify themselves or convince others with their perspectives. Reasoning in online discussions is expectedly to be different from doing so offline, as one often communicates with others anonymously and asynchronously in such contexts (e.g. Reddit discussions). The purpose of this paper is to investigate people's reasoning behavior in online environments focusing on how they justify their perspectives.Design/methodology/approachIn this study, the authors examined how a subreddit Change My View (CMV) users offer their opinions and justify them through the lens of argumentation and reasoning. The authors annotated, 330 Reddit discussion original posts (OPs) to identify claims, rationales and supports for reasoning, i.e. personal experiences, definitions, domain expertise and external sources. The authors investigated the correlations among the occurrences of these supporting statements and whether they are related to the topics of the posts.FindingsThe findings suggest that if people mention their domain expertise, they tend to provide related personal experiences as well. Additionally, if the participants talk about the topic of domestic politics, they tend to utilize their personal experiences.Research limitations/implicationsFurther research may be conducted to help system designers. System designers (e.g. online debate systems, collective decision-making systems, etc.) may benefit from the findings to design systems by considering commonly used supporting statements, which may enhance people's reasoning and argumentation processes. The sample size is a small sample. The authors acknowledge that the small sample size of the study may limit the generalizability of the findings; however, it is still acceptable compared to the existing literature. One future study could be annotating a larger dataset to further probe the use of supporting statements in online reasoning.Practical implicationsThe authors' findings might be useful to understand how Reddit users are justifying their opinions as the reflection of their reasoning processes. In order to contribute further research in argumentation and reasoning in online platforms, the authors make the annotated dataset publicly available.Originality/valueTo best of the authors' knowledge, this study was one of a few studies whose purpose is to understand Reddit CMV users' reasoning processes. To understand how online users offer their reasons while providing their ideas is important to have effective communication processes and to improve online discussion experiences which are very common in today's digital era.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/OIR-08-2020-0330