Social media such as microblogs (Twitter™) allow more people to disclose more personal and private information more frequently to more others than ever before. But what is the nature of, and what factors influence, those disclosures? Applying concepts from research and theory on self-disclosure research and microblogging, this study analyses 3751 tweets, with nearly half including disclosures, over a three-day period. At the user level, user-controlled boundary impermeability varied by user gender, feed identity (parenting, social media professional), and their interaction. At the tweet level, tweet valence, presence of disclosure, and front- or back-stage disclosure were variously influenced by user gender, Twitter feed identity, interactions between them, and boundary impermeability. Social construction of gender roles and social identities, as well as individual tendencies, and possibly communication contexts, are reflected in the valence, presence, and stage of disclosures in microblog content. © 2013 Elsevier Ltd. All rights reserved.