This disclosure describes a computing system that automatically detects users in visual proximity and adds the users to a private collaboration space enabling the users to share digital content. In one example, the computing system includes a video processing engine configured to detect, from first image data representative of a first physical environment that includes a second user, the second user, wherein the first image data is captured by an image capture system of a head-mounted display (HMD) worn by a first user. The computing system also includes a collaboration application configured to add, in response to detection of the second user, the second user to a set of users associated with a private collaboration space in which the set of users access shared digital content, wherein the set of users includes the first user.