This book interrogates the thin ideal in pro-anorexia online spaces and the way in which it operates on a continuum with everyday discourses around thinness. Since their inception in the late twentieth century, pro-anorexia online spaces have courted controversy: they have been vilified by the media and deleted by Internet moderators. This book explores the phenomenon during its tipping point where it migrated from websites and discussion forums to image-centric social media platforms - all the while seeking to circumvent censorship by, for instance, repudiating 'pro-ana' or adopting hashtags to obfuscate content. The author argues that instead of being driven further underground, 'pro-ana' is blurring the boundaries between normative and deviant conceptions of thinness. Situating the phenomenon in relation to accepted constructions of thinness, promulgated by establishments as far ranging as medicine and women's magazines, this book asks if 'pro-ana' holds the potential to critique that which has long been considered normal: the culture of compulsory thinness. Engaging with debates including the current climate of postfeminism and neoliberalism, digital censorship, the pre-eminence of white, middle-class, heterofemininity, and the articulation of pain in realising the thin ideal, Negotiating Thinness Online examines what happens when the margins and the mainstream merge.