It is widely used as a pH indicator (yellow at pH 3.0 purple at pH 4.6) tracking dye in agarosepolyacrylamide gel electrophoresis (migrates 9-60 bp in DNA gels) and in microscopy staining.

Its primary purpose is to provide sharp color transitions for acid-base titrations and visualize biomolecule migration in gels due to its low molecular weight and solubility in aqueousorganic media.

Bromophenol blue (C19H10Br4O5S) is a synthetic triphenylmethane dye appearing as a pink to red crystalline powder featuring a central benzoxathiole dioxide core with two 35-dibromo-4-hydroxyphenyl substituents odorless with density 2.2 gcm3 and melting point 279C.