Barrel-aged beer is a type of beer that has been matured in wooden barrels, often previously used for aging spirits like whiskey or rum. This process allows the beer to absorb flavors from the wood and any residual liquids, resulting in a complex taste profile. The aging process can also enhance the beer's aroma and mouthfeel. The duration of aging can vary, typically ranging from a few months to several years. During this time, the beer undergoes chemical changes that can develop unique characteristics, such as notes of vanilla, oak, or dried fruit. Barrel-aged beers are often released in limited quantities and are popular among craft beer enthusiasts.