In internet experiments on auditory perception, playback devices may be a confounding variable reducing internal validity. A test procedure to remotely control multiple characteristics of playback devices does not currently exist. Thus, the main goals of this study were to (a) develop and (b) validate a comprehensive, efficient and easy-to-handle test procedure for the reliable identification of playback equipment and its acoustical features in online experiments. Based on a counting task paradigm and psychoacoustic effects, the Headphone and Loudspeaker Test (HALT) was developed with which researchers can standardize loudness adjustments, detect stereo/mono as well as headphone/loudspeaker playback, and assess lower frequency limits. In a first laboratory study (N = 40), HALT was evaluated with four different playback devices (circumaural and intra-aural headphones; external and laptop loudspeakers). Beforehand, the acoustical properties of all playback devices had been measured (e.g., sound pressure level, frequency response). In a final step, the procedure was validated by an internet-based study (N = 211). HALT is assumed to be a reliable, comprehensive, and efficient procedure to remotely control playback devices and listening conditions. In the conclusion, we offer suggestions for an ideal routine for researchers to adapt.