Backrooms, director Kane Parsons' film adaptation of his viral YouTube horror series, will begin streaming on HBO Max on 25 September, roughly four months after its cinema debut. The film has become the year's second major horror sensation driven by an online creator, following Curry Barker's Obsession, and its move to streaming caps a remarkable theatrical run that saw it break records for its distributor.

The film earned a Certified Fresh 87% score on Rotten Tomatoes and grossed over $394 million worldwide from a reported budget of under $10 million, making it the highest-grossing release in A24's history, surpassing Marty Supreme. It stars Chiwetel Ejiofor as Clark, a struggling furniture store owner who discovers a portal to an endless liminal dimension in his shop's basement, and Renate Reinsve as his therapist Mary, who follows him into the strange world to bring him home. Mark Duplass, Finn Bennett and Lukita Maxwell also feature in the screenplay, written by Will Soodik.