Acidifiers are compounds classified as organic or inorganic acids. Organic acids include formic, fumaric, lactic, benzoic, propionic, and citric acids. Inorganic acids include hydrochloric, sulfuric, and phosphoric acids. Salts of acids also have been used as acidifiers, including calcium-formate, potassium-diformate, sodium-diformate, and sodium-fumarate. Blends of acidifiers are often commercially available because organic and inorganic acids may have a synergistic effect. In addition, some commercial acidifiers contain protected acids that are coated with fatty acids or other molecules, mainly to allow the release of the acid in a targeted location in the gut with the goal to improve effectiveness.

The mode of action of dietary acidifiers has not been fully understood, but several mechanisms have been proposed. Acidifiers are believed to enhance growth performance via pH reduction in the digestive tract, which improves nutrient digestibility and promotes growth of beneficial bacterial while inhibiting pathogenic bacteria