Coal gasification is recognized as the core technology of clean coal utilization that exhibits significant advantages in hydrogen-rich syngas production and CO₂ emission reduction. This review briefly discusses the recent research progress on various coal gasification techniques, including conventional coal gasification (fixed bed, fluidized bed, and entrained bed gasification) and relatively new coal gasification (supercritical water gasification, plasma gasification, chemical-looping gasification, and decoupling gasification) in terms of their gasifiers, process parameters (such as coal type, temperature, pressure, gasification agents, catalysts, etc.), advantages, and challenges. The capacity and potential of hydrogen production through different coal gasification technologies are also systematically analyzed. In this regard, the decoupling gasification technology based on pyrolysis, coal char–CO₂ gasification, and CO shift reaction shows remarkable features in improving comprehensive utilization of coal, low-energy capture and conversion of CO₂, as well as efficient hydrogen production. As the key unit of decoupling gasification, this work also reviews recent research advances (2019–2023) in coal char–CO₂ gasification, the influence of different factors such as coal type, gasification agent composition, temperature, pressure, particle size, and catalyst on the char–CO₂ gasification performance are studied, and its reaction kinetics are also outlined. This review serves as guidance for further excavating the potential of gasification technology in promoting clean fuel production and mitigating greenhouse gas emissions.