Steam methane reforming (SMR) has been adopted for the mass production of hydrogen that has been actively used in various industrial processes for several decades. Currently, the demand for hydrogen for small-scale domestic and vehicular applications is growing rapidly. Although essential technical elements are similar at the industrial and retail levels, large-scale centralized SMR techniques do not apply to small-scale distributed SMR systems owing to the difference in their production capacity and purposes. In this review, we summarize the state-of-the-art centralized and distributed SMR processes for large- and small-scale hydrogen production. No review has been reported on the differences and difficulties in SRM technology according to productivity. By categorizing conventional and new technologies and presenting practical issues according to production capacity, this review will contribute to the rapid adoption of decentralized SMR based hydrogen production systems.