What is the Difference Between a Stout and Porter?

What exactly is the difference between a porter and a stout? Great question! 

Nowadays it’s actually pretty hard to tell. Porters have deviated so much from its origins that it is now almost indistinguishable from stout. That said, it didn't start that way.

In the1800s a "stout" was technically a stronger – or stouter – version of a porter, which was a common brown beer.  So basically was a high ABV porter.  And brown stout was . . . a stout brown beer. So understandably, things quickly got muddled. Historians have found that many British porters and brown stouts in the early 19th century used identical recipes (that pretty much solves the case of the roasted barley myth.¹). In 1817 Daniel Wheeler invented a technique for roasting malt until it looked like espresso (now known as ‘black patent’). While England was still enjoying their porters based on brown malt, up in Ireland, Dublin breweries embraced the use of black malts. Combined with Dublin’s soft water, the resulting beer was dry and sharp. Hello Irish Stout.

To help disambiguate Stouts from Porters in the eyes of a very confused craft beer loving public, many American craft breweries label their more aggressive dark beer as the Stout, while their softer, smoother, lower alcohol content dark beer is the Porter. Breweries like Bells, Deschutes, and Stone Brewing tend to follow this general rule of thumb. Thank you for setting us all straight.