Benzoic-d5 acid is widely used as an internal standard in nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) due to its deuterated structure, which provides a stable reference for analytical measurements. It is particularly valuable in quantitative analysis of organic compounds, ensuring accuracy in detecting and measuring trace substances. Additionally, it serves as a labeled compound in metabolic studies, helping researchers track biochemical pathways and understand drug metabolism. Its application extends to the pharmaceutical industry, where it aids in the development and quality control of drugs by providing precise analytical benchmarks.