Here's a quick summary of the unsigned majority opinion (called a "per curiam"), joined by all the Justices except Justice Gorsuch (who concurred in the result, but with a different analysis) and (in part) Justice Sotomayor:
[1.] The Court expresses some doubt about whether the law triggers First Amendment scrutiny at all. The Court views the law as regulating "corporate control" over TikTok, rather than restricting speech directly, which makes it unclear (in the Court's view) whether the law should be treated as a "direct regulation" of expression.
The Court recognizes that " the Act's prohibitions, TikTok-specific designation, and divestiture requirement 'impose a disproportionate burden upon' their First Amendment activities," and acknowledges that "an effective ban on a social media platform with 170 million U. S. users certainly burdens those users' expressive activity in a non-trivial way." But while the law "will burden various First Amendment activities, including content moderation, content generation, access to a distinct medium for expression, association with another speaker or preferred editor, and receipt of information and ideas,"
