CPRG is commonly used in molecular biology microbiology and cell biology for reporter gene assays screening recombinant bacteria and quantifying gene expression driven by the lacZ gene.

The purpose of CPRG is to detect and measure beta-galactosidase enzyme activity in biological and microbiological assays.

Chlorophenol Red-beta-D-galactopyranoside (CPRG) is a chromogenic substrate that is cleaved by the enzyme beta-galactosidase producing a visible color change from orange to red or purple.