Naphthol AS-D is widely used as a coupling component in the production of azo dyes, which are essential for coloring textiles, leather, and paper. It forms stable, vibrant dyes when combined with diazonium salts, making it valuable in the textile industry for creating a range of shades, particularly reds and oranges. Additionally, it is employed in histology and cytology as a staining agent to identify specific tissues or cellular components under microscopic examination. Its ability to react with other compounds to produce distinct colors also makes it useful in analytical chemistry for detecting and quantifying various substances.