Fiducial marker tracking is a popular low-cost approach for enabling tangible user interfaces (TUIs). However, in previous marker tracking-based TUIs, the paper on which markers are typically printed on has rarely been utilized beyond serving as the medium for printing markers on. Paper Tags is a class of tangible desktop input devices based on fiducial marker tracking that are enhanced by exploiting the tangibility of markers’ paper component, i.e., tangible paper markers. Paper Tags can be a versatile yet low-cost do-it-yourself (DIY) approach for augmenting the standard desktop interface, without requiring additional complex hardware.