Bitters are made from soaking herbs, spices, fruits, or other botanicals with a clear, high-proof alcohol. Used sparingly due to their concentrated bitter/bittersweet flavours, bitters are loved by mixologists for their ability to add complexity to drinks.

The history of bitters is as old as the history of alcohol. The ancient Egyptians infused medicinal herbs in wine, the Middle Ages saw the birth of alcohol-based medical tonics being used in traditional remedies and the commercialisation of Angostura bitters in Venezuela in 1824.

Common botanicals involved in the production of bitters include orange peel, cassia bark, cascarilla, gentian root, and cinchona bark. These give different groups of bitters, but the two main groups being digestive and cocktail. Digestive bitters, such as Aperol, Fernet Branca and Jägermeiste are traditionally drunk after consuming a meal as they help with digestion. Cocktail bitters, such as Angostura, Boker's and Peychaud's are used to enhance the flavour of drinks.

Bitters usually contain more than 30% ABV. However, given the potency of cocktail bitters and the very small amounts which are added into a drink, these are sold as non-alcoholic products.