Bitters (also known as Cocktail Bitters) are an infusion of roots, bark, herbs and spices, usually in alcohol, that are legally classified as non-potable. This allows them to be sold in places that might not normally be able to sell alcohol, such as grocery stores. They are much more concentrated in flavor and bitterness than [ingredient=amaro Amari], but share flavor profiles and ingredients. Cocktail Bitters are usually dispensed into drinks by the drop or dash. They typically lack sugar (other than to color the liquid), and are high in alcohol, some approaching 90 proof.

The classic bittering agents include things like chinchona bark (the source of quinine), gentian root, wormwood, quassia bark, and angostura bark. Flavorings can include anything from citrus to cardamom to clove and cinnamon and licorice. Some modern bitters have cacao nibs or even chile peppers in them!

Some well known brands of cocktail bitters include:

• [ingredient=angostura Angostura] and [ingredient=angostura Angostura Orange]
• [ingredient=bittermens Bittermens]
• [ingredient=bitter-end The Bitter End]
• [ingredient=bitter-truth The Bitter Truth]
• [ingredient=bokers Boker's Bitters]
• [ingredient=fee-brothers Fee Brothers]
• [ingredient=peychauds-bitters Peychaud's]
• [ingredient=regans-orange-bitters Regans' Orange Bitters #6]

Cocktail bitters are an indispensable ingredient in most cocktails. In fact, the first use of the word cocktail as we know it was a recipe that included cocktail bitters — it was also known as a bittered sling. Even today, there are very few cocktails that are not improved by a judicious addition of bitters.