Duff Beer is the most popular brand of beer in Springfield. It is Homer's favorite beer and is enthusiastically promoted by Duffman, the company's mascot.

The quality of Duff appears to be standard for mass quantity supply beer. Strict regulations are supposedly maintained at Quality Assurance. Such a foothold for good supply may be the only filter as portions of Duff Beer contaminated by rats, body parts and even Hitler's head have been spotted.

Duff was endorsed during the Kennedy/Nixon debates by Kennedy, an idea that was then stolen by Nixon when he also tried to declare his support for 'that particular beer (which no one believed for a moment).

When Homer tours the Duff Brewery a pipeline is seen splitting freshly-brewed beer into the Duff, Duff Dry and Duff Lite tanks, implying they are the same beer with different labels. Duff tie-in products include a Duff Beer Suitcase, Duff "Gummy Beers" candy, and Duff Beer Calendars.