“Unfriended,” a horror movie for the social media age, has a premise that invites mockery: six teens on a Skype chat are harassed by what may be a supernatural entity. But while the tech is new, the tropes are familiar and potent. After all, the idea of getting a Facebook message from a dead person is just as creepy as — and no sillier than — the idea of getting a phone call from one.

First-time director Levan Gabriadze wins points for portraying real-life computer usage more authentically than any movie I’ve ever seen — a significant step in getting us to suspend our disbelief, since the whole thing takes place on the main girl’s laptop (all we see is her Skype video chats, Facebook page, instant messages, Gmail, etc.). The story, which might not actually make any sense, is one of those “I know what you did last summer” things, and it loses its way when it shifts from being about typical teens involved in typical mischief to being about unusually psychopathic teens who are awful. The mind games are more eerie than scary, too. But the film commits to its premise so thoroughly that you can almost buy it.

C+ (1 hr., 22 min.; R, a lot of harsh profanity, some sexual dialogue, mild sexuality, brief disturbing violent images.)