The name “IPA” is irrepressible in its marketability. It is, as Brooklyn Brewery’s beer scholar and brewmaster Garrett Oliver puts it, “the burger that every chef has to put on the menu but doesn’t want to.” The hamburger, it turns out, is an apt comparison for a beer style that has become as ubiquitous as America’s favorite sandwich.

“If you ask Dr. Bart Watson, ‘What’s the next IPA?’ He will most certainly tell you, ‘An IPA,’” says John Mallett, vice president at Bell’s Brewery in Kalamazoo, Michigan. The question now is, What kind?

Watson, chief economist and statistician for the Brewers Association, reports that currently, IPA controls a 40.3 percent share of the volume of beer made by independent craft brewers in the United States; last year at this time, it was 37.2 percent. Which is to say, if a brightly colored, cartoon-festooned can reads “IPA,” it will sell, so much so that these three letters have been extended to beers that have little to do with the classic definition of India Pale Ale (a dry, strong bitter pale ale with a brightly aromatic hop profile), one that’s been around since the mid-1800s. More than any other genre of beer, the IPA category has unabashedly been bent to the will of its devotees, launching an astonishing number of subgenres, ranging from the OG boldly bitter West Coast IPA to the fruity, cloudy New England IPA (aka Hazy IPA, aka Juicy IPA) to the ultrasweet Milkshake IPA to the razorlike Brut IPA to, most recently, the ever-popular Low-Cal IPA, a category that challenges the very tenets of the IPA set forth decades ago.

“Just because you liked a style at one point in time doesn’t mean that that’s the style forever,” says Craig Wathen, who with his wife and co-owner Beth, has championed IPAs—particularly those from the West Coast—at their City Beer Store in San Francisco since 2006. “For me, this style has always been evolving, and I would say improving,” he says. “It’s a category that can experiment, expand and go in different directions.”

Beyond the obvious reasons a brewer might decide to make an IPA, the style’s natural character as a meditation on the mighty hop has captivated new talent looking to make a mark. The boom in hop varieties over the past 15 years has given brewers an unbelievable palette to paint with. This, along with unbridled experimentation, is what has given rise to such diversity within the IPA category. But the proliferation of the New England IPA, and now the Low-Cal IPA, signals something that goes beyond innovation: It shows the true power of the IPA brand, and its ability to be whatever the consumer wants it to be.

In February, Bell’s, led by Mallett and head of brewing innovation, Andy Farrell, shocked many of its followers when it released Light Hearted Ale, a low-calorie version of its cornerstone IPA, Two Hearted Ale, a category stalwart since 1994. That a brewery with Bell's reputation—along with other marquee IPA producers like Deschutes, Firestone Walker and Dogfish Head—would move into this sector is a sign of just how much the market has changed.

In a way, the Low-Cal IPA is simply finishing what the Session IPA started a dozen years ago. The latter was billed as a lower-alcohol take on the IPA, which by then was dominated by brawnier brews that tested the upper limits of what might be deemed appropriate for the style (consider Ninkasi’s Tricerahops Double IPA, clocking in at nearly 100 IBUs and 9 percent alcohol). Jeremy Kosmicki, the head brewer at Founders, remembers his first go at the brewery’s now-iconic Session IPA, Founders All-Day IPA. (It took “20 stabs” to nail the recipe, he notes.) He sees that evolution, and now the current vogue to go even lighter, as part of a pendulum swing in tastes.

“It’s about having that staple, that easy-drinking style of beer,” says Kosmicki. “It’s not the Budweiser consumer that’s drinking it, but it’s the evolution of the craft drinker.”

The thing is, the IPA’s evolution isn’t linear. For the past half-decade, the biggest news in IPA has been the rise of the New England IPA as the standard-bearer for the genre, unseating the bold and bitter West Coast style that kicked off the IPA’s run. The New England IPA is not lower in alcohol, nor is it lower in calories, but its popularity has signaled a softening of the IPA’s rough edges that has seemed to, like the Session IPA, broaden the audience.

“I remember when hazy beers first started and all the old brewers were saying, ‘Those brewers are just lazy,’” says Vinnie Cilurzo, of Sonoma’s Russian River Brewing Co. “But… There’s something called gravity, and getting that protein to stay suspended is tough.” Cilurzo played a significant role in hewing the definition of a West Coast IPA with his Pliny the Elder, which he’s been making since 1999. But like any good businessman, he’s attuned to the moods of the market. He now makes two hazy IPAs: Tempo Change, since 2018, and Mind Circus, since 2019. While Pliny is still the brewery’s bestseller by about tenfold, Cilurzo has seen the IPA genre change enough that he knows making them requires a certain ability to adapt. “We aren’t so pig-headed to think Pliny is this forever beer,” says Cilurzo. “If it started to slow down and Mind Circus started to take off, Natalie [his wife and co-owner] and I wouldn’t be resistant to that—we’d give people what they wanted.”

Shortly after the breakneck rise of the New England IPA, the Milkshake IPA appeared as a hazy IPA taken to a new extreme via the addition of lactose in the build. The sugar doesn’t ferment out in the brewing process, leaving a saccharine creaminess to the beer. Instead of going ever more bitter, like the previous generation, the Milkshake IPA turned up the volume on the texture. Intensely sweet and fruity, the style dramatically called into question what can viably be deemed an IPA.

Curiously, around the same time the Milkshake IPA arrived, so did its polar opposite: the Brut IPA. “The shortest-lived style was more than parabolic; Brut IPA lasted about nine months,” says Oliver of Brooklyn Brewery. “It’s basically a saison made by adding an enzyme that would ferment all the sugar. Most beer has 2.5 percent [residual sugar], which is dry, but these would be 0 percent. The problem was, they didn’t taste good.” And perhaps he has a point, considering that many of the brewers who proffered the style (including Short’s, Ska and Ommegang) have now ceased in making it, veering off into the Low-Cal IPA market instead.

Of late, the Sour IPA has emerged as yet another boundary-questioning crossover IPA. At Grimm Artisanal Ales in Brooklyn, Lauren and Joe Grimm make a number of IPAs but have perhaps unconsciously sidestepped the magnetic pull of the IPA moniker with their Psychokinesis, a beer they describe as a “dry-hopped kettle sour.” But that doesn’t mean that the constant reorganizing of the IPA’s profile, its vernacular and its target consumer hasn’t left them a bit confused, too.

“I have to say, a dry-hopped sour is a sour IPA. I guess that's a great way of telling a customer that it's sour and has a lot of hops in it,” says Lauren, pausing to consider her conclusion. “But is a sour an IPA?”