From September to November, a certain beer style starts to fill shelves, tap menus and Instagram feeds across the country—and I’m not talking about pumpkin beer. Oktoberfest is everywhere. But for a beer with such ubiquity, few can agree on what it even is. 

Barring its more recent postmodern era, beer has long been governed by styles. Terms like pale ale, porter or doppelbock are shorthand for understanding the profile and process behind any given beer. But when it comes to Oktoberfest, there’s a vast flavor spectrum that the moniker could entail. 

“There are a variety of style interpretations you might find under an ‘Oktoberfest’ label, particularly in the United States,” says Brian Grossman, head brewer at Sierra Nevada Brewing Co. Ashleigh Carter, head brewer and co-owner at Denver’s Bierstadt Lagerhaus, agrees. “I don’t think the word ‘Oktoberfest’ can tell you exactly what it is. It’s divided into camps: festbier and märzen.”

Märzen has enjoyed the Oktoberfest association for longer. It’s a centuries-old German style traditionally made in spring, cellared and consumed through warmer months, and finished in the fall. That timeline made it a go-to for the first Oktoberfest celebration in 1810. It remained the Oktoberfest staple until 1990, when many German breweries switched to lighter festbiers.

“They began experimenting with lighter lagers as a response to shifting trends in beer and to align with the contemporary brewing practices and consumer preferences of the time,” says Katherine Benecke, certified Cicerone and general manager at New York’s Treadwell Park. “They were also cheaper to produce and quicker to brew.” 

Plus, as a lighter style, festbiers go down a lot easier at an event centered around guzzling as much beer as possible. Orangey-amber märzens are heavier and richer, often brewed with malts like Vienna and Munich, imparting graham cracker, caramel, toffee and biscuit notes. They’re also slightly stronger, ABV-wise. Festbiers, meanwhile, are golden-straw, grainy-sweet and easy-drinking. 

Order an Oktoberfest at the official festival in Munich, and you’ll be met with that light festbier. But in the States, Oktoberfests are still more commonly märzens. 

Case in point: Brooklyn’s KCBC’s annual Zøktoberfest release is a märzen. Co-founder Zack Kinney says the beer, which he was homebrewing before the brewery opened in 2016, was born by “following in the footsteps of what I saw American craft brewers doing at the time.” Indeed, older craft breweries like Sam Adams and Sierra Nevada have long made märzens as their Oktoberfests, solidifying the link between the biscuity beer and the fall season. Bierstadt and Cleveland’s Great Lakes Brewing Co. also still honor the märzen path. 

“We do what I would consider the more traditional Oktoberfest,” says Great Lakes brand coordinator and certified advanced Cicerone Michael Williams. “We’ve been around since 1988, and that’s the way most American craft breweries [have] rolled with it.”

But the varying styles do not neatly adhere to an American-European divide. Festbiers are increasingly cropping up under the Oktoberfest moniker at American breweries, too, which Carter attributes to more people experiencing Oktoberfest firsthand, better beer education and a growing, diversifying interest in lagers—why stick to märzen when you can add festbier to your lineup and demonstrate the nuances of lagers? 

In fact, KCBC recently added a festbier to its Oktoberfest-timed offerings; in New Orleans, Brieux Carré likewise makes both a traditional märzen and a festbier. Head brewer Charles Hall says they benefit from being a taproom-focused brewery, where staff can explain differences to guests as they try both styles. And while he stands behind both, he does have an opinion on what ought to be considered the Oktoberfest. “I think the modern festbier should be the default for ‘Oktoberfest’ beer, since that’s typically what is served in Germany.”

Head brewer at Pittsburgh’s Hop Farm Brewing Co. Matthew Gouwens agrees. “Festbier is an Oktoberfest style,” he says. To him, märzen actually makes more sense as a spring beer because of its brewing history.

In perhaps the strongest showing of the American Oktoberfest evolution, Sierra Nevada, a name younger breweries reference when explaining their decision to brew märzen, has taken to vacillating its annual brew between märzens and festbiers. “The beer under our ‘Oktoberfest’ label is different each year because we work with a different German collaborator each year,” says Grossman. This year, they’ve made a festbier with Brauerei Gutmann. 

If the brand that is partly responsible for establishing the American craft blueprint for Oktoberfest beers now brews both styles under the Oktoberfest name, it might be time to accept a less-tidy definition of the style. 

“I think we can paint a broad-stroke definition [for] beer drinkers,” says beer judge and writer Joshua Weikert. “If it’s a pale to amber lager with a bready-toasty profile and a little European hops character, it can plausibly be called ‘Oktoberfest.’”