While we have witnessed a flurry of research on the history, politics, and legality of externalization policies, conceptual work has been relatively scarce. Against this backdrop, we put forward a taxonomy of externalization policies, distinguishing the spaces in which states aim to control human movements and limit their legal obligations towards people seeking protection as well as the means by which states exercise power. Essentially, states have strived to control territorial space through physical obstacles and digital innovation; legal space through policies of inadmissibility and practices of irresponsibility; diplomatic space through bilateral and multilateral cooperation; and influence mobility aspirations by targeting the mental space of potential migrants. The evolution of these four layers of refugee externalization implies supplementing biopolitics based on external migration control measures with transnational psychopolitics based on communicative strategies aiming to disincentivize departure by internalizing control. Published in online compendium “Externalizing Asylum: A Compendium of Scientific Knowledge” on 25 June 2024, https://externalizingasylum.info/a-taxonomy-of-externalization-policies/ A shorter version of this article was published in the “Forced Migration Studies Blog” (FluchtforschungsBlog) on 9 July 2024, https://fluchtforschung.net/a-taxonomy-of-externalization-policies/