The GLobal airglOW model, also known as GLOW, is a toolkit of subroutines and driver programs for performing calculations of optical emissions in the upper atmosphere, particularly the thermosphere and ionosphere, above about 100 km altitude. These emissions are caused by combinations of solar-driven photon processes, auroral precipitation, and chemical reactions. GLOW can calculate various spectral features for any combination of solar and/or auroral inputs, given a specification of the neutral atmosphere and the high-altitude ionosphere.