India Pale Ale, commonly known as IPA, is a hoppy beer style within the broader category of pale ale. The first known use of the term "India pale ale" is an advertisement in the Sydney Gazette and New South Wales Advertiser in 1829.
In the 1700s, during the long voyage around the Cape of Good Hope to India, beer did not fare well. Without refrigeration and pasteurization, beer would arrive in India flat and sour. George Hodgson at the Bow Brewery in East London took his pale ale recipe, increased the hop content considerably, and raised the alcohol content. The result was a very bitter, alcoholic, and sparkling pale ale that could survive the challenges of travel and shelf life in India.
The term IPA is common in the UK for low-gravity beers, for example Greene King IPA and Charles Wells Eagle IPA. IPAs with alcohol by volume of 4% or lower have been brewed in Britain since the First World War, when taxes on beer ingredients greatly increased and brewers responded by lowering the strength of their beers.
Canada and the United States
IPAs have a long history in Canada and the United States and many breweries there produce a version of the style. Contemporary American IPAs are typically brewed with distinctively American hops, such as Cascade, Centennial, Citra, Columbus, Chinook, Simcoe, Amarillo, Tomahawk, Warrior, and Nugget.
East Coast IPAs are distinguished from West Coast IPAs by a stronger malt presence which balances the intensity of the hops, whereas the latter emphasizes the hops more, possibly because of the proximity of West Coast breweries to hop fields in the Pacific Northwest. East Coast breweries rely more on spicier European hops and specialty malts than those on the West Coast.
Imperial IPAs (also referred to as Double IPAs and Triple IPAs) are a stronger, very hoppy variant of IPAs that typically have alcohol content above 7.5% by volume. The style is claimed to have originated with Vinnie Cilurzo, currently the owner of Russian River Brewing Company in Santa Rosa CA., in 1994 at the now-defunct Blind Pig Brewery in Temecula, California.
Session IPA describes a category of beers marketed for their hop-dominant flavor profiles at "sessionable" levels of alcohol. While this is typically between 3.2% and 4.6% ABV, a few have stretched the definition into ABV levels of over 5%. It is differentiated from American Pale Ale by typically being lower in alcohol and usually having more hop-dominant profiles.