ARTag is a fiduciary marker system to support augmented reality. It can be used to make it easy to make virtual objects, games, and animations appear to enter the real world. Like the earlier ARToolKit system, it allows for video tracking capabilities that calculate the real camera position and orientation relative to square physical markers in real time. Once the real camera position is known a virtual camera can be positioned at the same point and 3D computer graphics models drawn exactly overlaid on the real marker. It thus addresses two of the key problems in Augmented Reality: viewpoint tracking and virtual object interaction.
An ARTag appears on the Mars Science Laboratory. A similar technique is used by NASA's Spacecraft 3D smartphone app as an educational outreach tool.
ARTag is supported by the open source Goblin XNA software.