Reactive Blue 4 is widely used in the textile industry for dyeing cellulosic fibers such as cotton, rayon, and linen. It forms strong covalent bonds with the fiber under alkaline conditions, resulting in excellent color fastness to washing and light exposure. This dye is particularly effective in batch and continuous dyeing processes where bright blue shades are required. It is also employed in the paper industry to color paper products, offering good uniformity and intensity. Due to its reactive nature, it minimizes dye wastage and improves uptake efficiency, making it suitable for eco-friendly dyeing processes when combined with proper wastewater treatment. In addition, Reactive Blue 4 has been used in research settings as a model compound for studying dye degradation, adsorption behavior, and wastewater treatment methods, especially in evaluating the efficiency of decolorization techniques like ozonation, photocatalysis, and biological treatment.