DMSO-d6 (deuterated dimethyl sulfoxide) is a specialty solvent primarily used in nuclear magnetic resonance (NMR) spectroscopy. Its high deuterium content (typically >99.8%) eliminates solvent proton signals, enabling clear analysis of samples including organic molecules, proteins, polymers, and materials. It often includes ~0.03% TMS as an internal chemical shift reference. While regular DMSO has broader applications (e.g., cryopreservation, drug delivery), DMSO-d6’s high cost and isotopic specificity limit it to NMR and related spectroscopic techniques.