[1] It premiered at South by Southwest in March 2016 and was broadcast on HBO on January 23, 2017.

[2][3] Beware the Slenderman discusses the incident in which two girls attempted to murder one of their friends in an attempt to appease Slender Man, a fictional monster who originated from an Internet phenomenon called "creepypasta".

The documentary was shot over eighteen months and contains interviews with the families of the two would-be murderers.

The film makes use of various YouTube videos to do with Slender Man, in particular footage from Marble Hornets and Tribe Twelve.

[4] Metacritic rated the film as "generally favorable" with a critic score of 78 [clarification needed][5]