Sulfanilic acid is primarily used in the production of dyes and pigments, particularly azo dyes, which are widely applied in textiles, paper, and leather industries. It serves as a key intermediate in synthesizing compounds like methyl orange, an indicator in acid-base titrations. Additionally, it is utilized in the manufacture of sulfa drugs, a class of antibiotics effective against bacterial infections. In analytical chemistry, sulfanilic acid is employed in the Griess test for detecting nitrite ions, making it valuable in water quality analysis and environmental monitoring. Its derivatives also find applications in the food industry as preservatives and in the production of optical brighteners for detergents.