Internet-based research conducted in partnership with paid crowdworkers and volunteer citizen scientists is an increasingly common method for collecting data from large, diverse populations. We wanted to leverage web-based citizen science to gain insights into phenomena that are part of people’s everyday lives. To do this, we developed the concept of a Massive Open Online Diary (MOOD). A MOOD is a tool for capturing, storing and presenting short updates from multiple contributors on a particular topic. These updates are aggregated into public corpora that can be viewed, analysed and shared. MOODs offer a novel method for crowdsourcing diary-like data in a way that provides value for researchers, teachers and contributors. MOODs also come with unique community-building and ethical challenges. We describe the benefits and challenges of MOODs in relation to Errordiary.org, a MOOD we created to aid our exploration of human error
