Building from previous researchers’ conceptions of queer technologies, we consider what it means to be a trans technology. This research study draws from interviews with Tumblr transition bloggers (n = 20), along with virtual ethnography, trans theory, and trans technological histories, using Tumblr as a case study to understand how social technologies can meet the needs of trans communities. Tumblr supported trans experiences by enabling users to change over time within a network of similar others, separate from their network of existing connections, and to embody (in a digital space) identities that would eventually become material. Further, before 2018 policy changes banning “adult” content, Tumblr upheld policies and an economic model that allowed erotic content needed for intersectional trans community building. We argue that these aspects made Tumblr a trans technology. We examine themes of temporality, openness, change, separation, realness, intersectionality, and erotics, along with considering social media platforms’ policies and economic models, to show how trans technologies can provide meaningful spaces for trans communities.