Abstract: We use personality theory to compare self-presentation between multiple Instagram accounts, investigating authenticity and consistency. Many studies claim social media promote inauthentic self-presentation focused on socially desirable traits. At the same time, affordances suggest that self-presentation should be relatively consistent within one social medium. For 88 participants, we examine personality traits for ’real Instagram’ (’Rinsta’) versus ’fake Instagram’ (’Finsta’) accounts, comparing these with people’s offline traits using mixed-methods. Counterintuitively, we find Finsta accounts often present socially undesirable traits. Furthermore, different accounts on the same social medium reveal quite different styles of self-presentation. Overall Finstas are more Extraverted, less Conscientious, and less Agreeable than Rinstas, although equally Neurotic as offline. Interviews indicate trait differences arise from differing audience perceptions. A large anonymous Rinsta audience promotes a carefully curated self. In contrast, a small but trusted Finsta audience can engender more authentic, but negative self-presentation. We discuss design and theory implications.