Cite as: 601 U. S. ____ (2024) 3 Syllabus over this critical step. Unless Freed was “possessed of state authority” to post city updates and register citizen concerns, Griffin, 378 U. S., at 135, his conduct is not attributable to the State. Importantly, Lindke must show more than that Freed had some authority to communicate with residents on behalf of Port Huron. The alleged censorship must be connected to speech on a matter within Freed’s bailiwick. There must be a tie between the official’s authority and “the gravamen of the plaintiff’s complaint.” Blum v. Yaretsky, 457 U. S. 991, 1003. To misuse power, one must possess it in the first place, and §1983 lists the potential sources: “statute, ordinance, regulation, custom, or usage.” Determining the scope of an official’s power requires careful attention to the relevant source of that power and what authority it reasonably encompasses. The threshold inquiry to establish state action is not whether making official announcements could fit within a job description but whether making such announcements is actually part of the job that the State entrusted the official to do. Pp. 9–12. (2) For social-media activity to constitute state action, an official must not only have state authority, he must also purport to use it. If the official does not speak in furtherance of his official responsibilities, he speaks with his own voice. Here, if Freed’s account had carried a label—e.g., “this is the personal page of James R. Freed”—he would be entitled to a heavy presumption that all of his posts were personal, but Freed’s page was not designated either “personal” or “official.” The ambiguity surrounding Freed’s page requires a fact-specific undertaking in which posts’ content and function are the most important considerations. A post that expressly invokes state authority to make an announcement not available elsewhere is official, while a post that merely repeats or shares otherwise available information is more likely personal. Lest any official lose the right to speak about public affairs in his personal capacity, the plaintiff must show that the official purports to exercise state authority in specific posts. The nature of the social-media technology matters to this analysis. For example, because Facebook’s blocking tool operates on a page-wide basis, a court would have to consider whether Freed had engaged in state action with respect to any post on which Lindke wished to comment. Pp. 12–15. 37 F. 4th 1199, vacated and remanded. BARRETT, J., delivered the opinion for a unanimous Court.