In this new documentary from the film group Field of Vision, the leader of a session on content moderation asks a simple question: when you open Facebook, you don’t, as a rule, see pornography. Why?

“The Moderators” explores the answer, going inside on office in India where the process happens. Directed by Ciaran Cassidy and Adrian Chen, a journalist who has written about the moderation process, the documentary is a window into a largely hidden part of the internet work force: employees who sit in an office and make decisions about whether to remove explicit photos, or who examine dating site profiles to weed out fakes.

The work turns increasingly bleak, and a group leader explains what it all means for the staff when he tells them they may find some images “disturbing,” before providing examples.

“Be mentally prepared for your job,” he warns.