Jopen Koyt is a strong gruit ale brewed according to a recipe from 1407, discovered in Haarlem's historical city ordinance. This medieval beer relies on no hops, instead employing an ancient herbal blend in which sweet gale plays a central role. The result is a complex, spiced ale with a full body that opens sweet and closes with subtle sourness.

Brewed at the Jopenkerk in Haarlem—a converted church that has served as the brewery's home since 2010—the Koyt stands as a living recreation of pre-hop brewing tradition. It remains a singular expression of medieval Dutch brewing craft.