2 MOODY v. NETCHOICE, LLC Syllabus court held that the obligation to explain “millions of [decisions] per day” is “unduly burdensome and likely to chill platforms’ protected speech.” 34 F. 4th, at 1230. The Fifth Circuit disagreed across the board, and so reversed the preliminary injunction of the Texas law. In that court’s view, the platforms’ content-moderation activities are “not speech” at all, and so do not implicate the First Amendment. 49 F. 4th 439, 466, 494. But even if those activities were expressive, the court determined the State could regulate them to advance its interest in “protecting a diversity of ideas.” Id., at 482. The court further held that the statute’s individualized-explanation provisions would likely survive, even assuming the platforms were engaged in speech. It found no undue burden under Zauderer because the platforms needed only to “scale up” a “complaint-and-appeal process” they already used. 49 F. 4th, at 487. Held: The judgments are vacated, and the cases are remanded, because neither the Eleventh Circuit nor the Fifth Circuit conducted a proper analysis of the facial First Amendment challenges to Florida and Texas laws regulating large internet platforms. Pp. 9–31. (a) NetChoice’s decision to litigate these cases as facial challenges comes at a cost. The Court has made facial challenges hard to win. In the First Amendment context, a plaintiff must show that “a substantial number of [the law’s] applications are unconstitutional, judged in relation to the statute’s plainly legitimate sweep.” Americans for Prosperity Foundation v. Bonta, 594 U. S. 595, 615. So far in these cases, no one has paid much attention to that issue. Analysis and arguments below focused mainly on how the laws applied to the content-moderation practices that giant social-media platforms use on their best-known services to filter, alter, or label their users’ posts, i.e., on how the laws applied to the likes of Facebook’s News Feed and YouTube’s homepage. They did not address the full range of activities the laws cover, and measure the constitutional against the unconstitutional applications. The proper analysis begins with an assessment of the state laws’ scope. The laws appear to apply beyond Facebook’s News Feed and its ilk. But it’s not clear to what extent, if at all, they affect social-media giants’ other services, like direct messaging, or what they have to say about other platforms and functions. And before a court can do anything else with these facial challenges, it must “determine what [the law] covers.” United States v. Hansen, 599 U. S. 762, 770. The next order of business is to decide which of the laws’ applications violate the First Amendment, and to measure them against the rest. For the content-moderation provisions, that means asking, as to every covered platform or function, whether there is an intrusion on pro-

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