Self-disclosure, the sharing of personal information between communication partners, has long been a topic of interest due to the large impact it plays in the development of interpersonal relationships (Altman & Taylor, 1973). As the use of computer-mediated communication (CMC) has increased, so has the interest in the impact it may have on self-disclosure and relationship development. Several theories have been posited to explain the impact that the medium of communication has on self-disclosure. Although some theories have predicted a negative impact of CMC on self-disclosure (Daft & Lengel, 1986; Kock, 2005), several researchers have found that CMC increases self-disclosure (McKenna & Bargh, 2000; Valkenberg & Peter, 2009a; Walther, 1996). This article discusses the main theories that explain the nature of online self-disclosure, the possible mechanisms by which CMC serves to increase self-disclosure, and impact that online self-disclosure has on interpersonal relationships and well-being.