Chlorophenol red β-D-galactopyranoside (CPRG) is widely used as a chromogenic substrate in biochemical assays, particularly for detecting β-galactosidase activity. In molecular biology, it is employed in reporter gene systems, where the presence of β-galactosidase leads to the hydrolysis of CPRG, producing a color change from yellow to red. This colorimetric shift allows for easy visualization and quantification of enzyme activity, making it a valuable tool in cloning, gene expression studies, and high-throughput screening. Additionally, CPRG is utilized in microbiology for identifying β-galactosidase-producing bacteria, aiding in microbial diagnostics and research. Its sensitivity and ease of use make it a preferred choice in various laboratory applications, including gene therapy efficiency assessments and related clinical tests.