An electrolysis system uses electricity to split water molecules into hydrogen and oxygen. In this process, the electrolysis system produces hydrogen, and the remaining oxygen escapes to the atmosphere or is captured or stored for use in industrial processes, or for other purposes. This study provides a detailed assessment of four major electrolysis technologies (alkaline water electrolysis, proton exchange membrane electrolysis, solid oxide electrolysis, and anion exchange membrane electrolysis), their characteristics, key players in the global electrolyser market, and recent trends that define electrolysis technology and market development. The scope of this study extends not only to the analysis of electrolysis technologies, but also to an overview of the availability of critical materials, shortages or disruptions in supply of which can prove challenging or even harmful for those markets/regions with limited excess platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, and osmium) and rare earth metals. Also, for two electrolysis technologies: alkaline water electrolysis and proton exchange membrane electrolysis, a comparison of efficiency and initial calculation of CAPEX for installations with medium and large installed capacities (5 and 100 MW) was presented.