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This paper analyzes decarbonization strategies for district heating and their carbon footprint based on two separate literature reviews. The first review evaluates 90 studies to identify and classify decarbonization strategies along the district heating supply chain using the Avoid-Shift-Improve (ASI) framework. To complement this, a multi-criteria decision analysis (MCDA) was applied based on six predefined criteria, enabling a structured scoring and comparison of the strategies. This combined approach allowed for their classification into high, medium, and low potential. High-potential strategies, such as heat pumps, combined heat and power (CHP), energy storage, geothermal, and digitalization, are identified for their substantial benefits. Medium-potential options, such as electric boilers, waste heat, solar thermal, building renovation, IoT, and temperature reduction show promise but face technical and economic barriers. Low-potential strategies, including biomass, hydrogen, nuclear, subsidies, and carbon capture and storage (CCS), face various implementation challenges. The study emphasizes the importance of combining demand reduction, innovative storage, smart grids, and site-specific energy sources to achieve sustainable district heating. Regional differences are noted: Scandinavia leads in decarbonization, Eastern Europe favors biomass, and Southern Europe shows potential for low-temperature networks. Recent research prioritizes heat pump efficiency and industrial waste heat, especially in relation to green electricity demand. The second review compares carbon footprints using 37 life cycle assessment (LCA) studies. Renewables-based systems emit the least, between −0.001 and 0.0909 kg CO 2 e/MJ of heat, with waste heat and geothermal performing best. Fossil fuel systems have the highest emissions, ranging from 0.04 to 0.31 kg CO 2 e/MJ. The findings contribute to the ongoing transition toward sustainable district heating and provides a foundation for future research in urban heat supply and energy policy, emphasizing the need for supporting measures and standardized methodologies to optimize decarbonization pathways. • Scandinavia leads in decarbonization of district heating systems. • Heat pumps, CHP, storage, and digitalization offer the highest decarbonization impact. • Waste heat and geothermal emit the least CO 2 , fossil fuels the most. • Eastern EU favors biomass, South EU leads in low-temp grids.