Methanol-D4 is primarily used as a deuterated solvent in nuclear magnetic resonance (NMR) spectroscopy. Its deuterium atoms provide a non-interfering background, making it ideal for analyzing the structure of organic compounds. It is also employed in research involving isotopic labeling to study reaction mechanisms and metabolic pathways. Additionally, Methanol-D4 finds application in the synthesis of deuterated pharmaceuticals, where it helps in tracing and understanding drug metabolism and distribution within biological systems.