Carbostyril 124 is primarily used as a fluorescent whitening agent in textile and paper industries. It enhances the visual brightness of fabrics and paper products by absorbing ultraviolet light and re-emitting it as blue visible light, counteracting yellowish tones and giving materials a cleaner, whiter appearance. It is especially effective in synthetic fiber treatments, including polyester and nylon, where it improves color clarity and overall aesthetic appeal. Additionally, it is utilized in some industrial coatings and plastics to maintain color stability and reduce aging effects under UV exposure. Its strong fluorescence and compatibility with various polymer systems make it suitable for high-performance applications requiring long-lasting whiteness and brightness.