7-(Diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester is a reagent featuring a 7-(diethylamino)coumarin and an NHS ester. The NHS ester is a highly activated carboxylic acid which readily reacts with amines under mild conditions to form amides. 7-(diethylamino)coumarin is a fluorophore which is used in a variety of applications such as in fluorescence assays or as a biomedical inhibitor.