Being a clean source of energy, hydrogen gas is in high demand in various industrial and commercial applications. However, the explosive nature of H-2 gas above 4% concentration makes it highly dangerous to store, transport and use. Further, the small size gas molecules of H-2 are prone to leak through the smallest possible holes and cracks. Hence, the detection of H-2 gas becomes essential even at trace levels. This article reviews various gas sensing strategies including methods, materials, and integrated systems available for the sensitive detection of H-2 gas for a bunch of different applications. The article also reviews some approaches which are available in the literature to detect parts per billion (ppb) level of H-2 gas concentrations. This review article aims at explaining the different aspects of H-2 gas sensing technology in a simple yet exhaustive manner. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.