The prevalence of social media blurs the boundaries between consumer and producer, work and play, and leads to new social roles, professions, and identities (e.g. blogger, YouTuber, micro-celebrity). However, we still lack a clear understanding of how people come to identify with these new roles and how individual professional development is digitally mediated. This paper presents a study based on Bilibili, a popular Chinese social media platform featuring user-generated videos, and highlights a professionalization process through which individuals consciously distinguish between the roles of uploaders and consumers, develop a shared work ethos around the role of the uploader, and, as uploaders, improve their technical-professional expertise. We conclude by discussing individualized professionalization as a concept that describes the bottom-up and community-based process of professional development for User Generated Content (UGC) taking place in contemporary digital media environments.