The term first appeared in the early 19th century as part of the development and spread of pale ale. Breweries would tend to designate beers as pale ale, while customers would commonly refer to the same beers as bitter, probably to differentiate them from other less noticeably hopped beers.

Bitters vary in colour from gold to dark amber and in strength from 3% to 7% alcohol. English bitter is widely considered by English drinkers to be the best beer in the world, as a result of its style being difficult to find elsewhere.

Drinkers tend to loosely group modern bitter into session or ordinary bitter (up to 4.1% abv), best or special bitter (between 4.2% and 4.7% abv) and strong bitter (4.8% abv and over). The term light ale is also often used to refer to a low alcohol bitter which is typically bottled.