4-Sulfophthalic acid is primarily used in the production of dyes and pigments, where it acts as an intermediate to create vivid and stable colorants for textiles, inks, and coatings. Its sulfonic acid group enhances water solubility, making it valuable in formulations requiring aqueous compatibility. Additionally, it is utilized in the synthesis of specialty polymers and resins, contributing to their improved adhesion, durability, and chemical resistance. In the field of electroplating, it serves as an additive to enhance the quality and uniformity of metal coatings. Its versatility also extends to the pharmaceutical industry, where it is employed in the preparation of certain active ingredients or excipients.