A kosher certification agency is an organization or certifying authority that grants a hechsher to ingredients, packaged foods, beverages, and certain materials, as well as food-service providers and facilities in which kosher food is prepared or served. This certification verifies that the ingredients, production process including all machinery, and/or food-service process complies with the standards of kashrut as stipulated in the Shulchan Arukh, the benchmark of religious Jewish law. The certification agency employs mashgichim to make periodic site visits and oversee the food-production or food-service process in order to verify ongoing compliance. Each agency has its own trademarked symbol that it allows manufacturers and food-service providers to display on their products or in-store certificates; use of this symbol can be revoked for non-compliance. Each agency typically has a "certifying rabbi" who determines the exact kashrut standards to be applied and oversees their implementation.

Kosher foods are foods that conform to the Jewish dietary regulations of kashrut. The laws of kashrut apply to food derived from living creatures and kosher foods are restricted to certain types of mammals, birds and fish meeting specific criteria; the flesh of any animals that do not meet these criteria is forbidden by the dietary laws. Furthermore, kosher mammals and birds must be slaughtered according to a process known as shechita and their blood may never be consumed and must be removed from the meat by a process of salting and soaking in water for the meat to be permissible for use. All plant-based products, including fruits, vegetables, grains, herbs and spices, are intrinsically kosher, although certain produce grown in the Land of Israel is subjected to other requirements, such as tithing, before it may be consumed.