Bluesky and the AT Protocol: Usable Decentralized Social Media Martin Kleppmann martin.kleppmann@cst.cam.ac.uk University of Cambridge Cambridge, UK Paul Frazee Jake Gold Jay Graber Daniel Holmgren Bluesky Social PBC United States Devin Ivy Jeromy Johnson Bryan Newbold Jaz Volpert Bluesky Social PBC United States ABSTRACT Bluesky is a new social network built upon the AT Protocol, a de- centralize