2 LINDKE v. FREED Syllabus the official both (1) possessed actual authority to speak on the State’s behalf on a particular matter, and (2) purported to exercise that authority when speaking in the relevant social-media posts. Pp. 5–15. (a) Section 1983 provides a cause of action against “[e]very person who, under color of any statute, ordinance, regulation, custom, or usage, of any State” deprives someone of a federal constitutional or statutory right. (Emphasis added.) Section 1983’s “under color of” text makes clear that it is a provision designed as a protection against acts attributable to a State, not those of a private person. In the run-ofthe-mill case, state action is easy to spot. Courts do not ordinarily pause to consider whether §1983 applies to the actions of police officers, public schools, or prison officials. Sometimes, however, the line between private conduct and state action is difficult to draw. In Griffin v. Maryland, 378 U. S. 130, for example, it was the source of the power, not the identity of the employer, which controlled in the case of a deputized sheriff who was held to have engaged in state action while employed by a privately owned amusement park. Since Griffin, most state-action precedents have grappled with whether a nominally private person engaged in state action, but this case requires analyzing whether a state official engaged in state action or functioned as a private citizen. Freed’s status as a state employee is not determinative. The distinction between private conduct and state action turns on substance, not labels: Private parties can act with the authority of the State, and state officials have private lives and their own constitutional rights—including the First Amendment right to speak about their jobs and exercise editorial control over speech and speakers on their personal platforms. Here, if Freed acted in his private capacity when he blocked Lindke and deleted his comments, he did not violate Lindke’s First Amendment rights—instead, he exercised his own. Pp. 5–8. (b) In the case of a public official using social media, a close look is definitely necessary to categorize conduct. In cases analogous to this one, precedent articulates principles to distinguish between personal and official communication in the social-media context. A public official’s social-media activity constitutes state action under §1983 only if the official (1) possessed actual authority to speak on the State’s behalf, and (2) purported to exercise that authority when he spoke on social media. The appearance and function of the social-media activity are relevant at the second step, but they cannot make up for a lack of state authority at the first. Pp. 8–15. (1) The test’s first prong is grounded in the bedrock requirement that “the conduct allegedly causing the deprivation of a federal right be fairly attributable to the State.” Lugar v. Edmondson Oil Co., 457 U. S. 922, 937 (emphasis added). Lindke’s focus on appearance skips