To describe (a) the conceptualization, purpose, and features of The American Cancer Society's Cancer Survivors Network® (CSN; http://csn.cancer.org ), (b) the ongoing two-phase evaluation process of CSN, and (c) the characteristics of CSN members.An online opt-in self-report survey of CSN members (N = 4762) was conducted and digital metrics of site use were collected.Annually, CSN attracts over 3.6 million unique users from over 200 countries/territories. Most commonly used site features are discussion boards (81.1%), the search function (63.8%), and the member resource library (50.2%). The survey sample is mostly female (69.6%), non-Hispanic white (84.1%), and self-identified as a cancer survivor (49.8%), or both cancer survivor and cancer caregiver (31.9%). A larger number of survey respondents reported head and neck cancer (12.5%), relative to cancer incidence/prevalence data.The volume of CSN traffic suggests high demand among cancer survivors and caregivers for informational and/or emotional support from other cancer survivors and caregivers. CSN may be particularly beneficial for individuals with rare cancers. Furthermore, this study documents a group of individuals whose cancer experience is multifaceted (e.g., survivors became caregivers or vice versa), and for whom CSN has the capacity to provide support at multiple points during their cancer experiences.CSN is a free, internet-based social networking site available to all cancer survivors and caregivers, worldwide. Evaluation of the site is ongoing and will be used to inform improvements to usability, reach, recruitment, retention, and potential health impact(s) of this valuable resource.