Sulfanilic acid is primarily used in the production of azo dyes, which are widely employed in the textile, paper, and leather industries for coloring purposes. It serves as a key intermediate in synthesizing dyes like methyl orange and Congo red, known for their vibrant and stable colors. Additionally, it is utilized in analytical chemistry as a reagent for detecting nitrites and in the preparation of sulfa drugs, which are antibiotics used to treat bacterial infections. Its role in organic synthesis and as a coupling agent in dye manufacturing highlights its industrial significance.