Bitter liqueur are a type of liqueur that is more bitter than other liqueurs. The bitterness is achieved by adding herbs, roots, citrus fruits, and other ingredients that contain gentians and aromatic compounds. Bitters typically range from 20% to 45% alcohol by volume, and can be consumed on their own or used as an ingredient in cocktails. Some of the most well-known bitters include Amaro, Campari, Fernet Branca, Angostura Bitters, and Chartreuse. Bitters are also used in cooking to add depth and complexity to various dishes and sauces.