Used as a substrate in molecular biology for detecting β-galactosidase activity. It is commonly applied in blue-white screening to identify recombinant bacteria. When cleaved by β-galactosidase, it produces an insoluble blue product, allowing for visual differentiation between colonies with and without the enzyme. This makes it valuable in cloning experiments, gene expression studies, and mutagenesis assays. It is also utilized in histochemistry and biochemistry research to localize and quantify β-galactosidase in cells and tissues.