m-Toluidine-4-sulfonic acid is primarily used as an intermediate in the synthesis of dyes and pigments, particularly azo dyes, which are widely employed in the textile, paper, and leather industries. Its sulfonic acid group enhances water solubility, making it valuable for creating dyes that adhere well to fabrics. Additionally, it is utilized in the production of organic compounds, including pharmaceuticals, where it serves as a building block for more complex molecules. The compound’s reactivity and structure also make it useful in research and development for synthesizing specialized chemicals.