Diablo 4 won't feature a cow level, at least at launch. Blizzard confirmed in an interview that there won't be a cow level in Diablo 4, as it wouldn't match with the tone and world of the game.

In an interview with Wowhead, a developer seemingly confirmed that there will not be a cow level, or an equivalent type of area, in Diablo 4 at launch. Blizzard cited the gritty and grounded world of Diablo 4 as the reason why things like a cow level, pets, or wings won't appear in the game. However, as the game exists and gets post-launch updates, Blizzard might loosen those restrictions.

The cow level refers to the hidden level in Diablo 2 called The Secret Cow Level, which features a ton of Hell Bovine enemies. Blizzard has regularly denied the existence of the cow level in the past, even putting a "There is no cow level" message in Diablo 2, but it seems to be true for Diablo 4. This level was popular for farming XP, since the cow enemies were relatively weak and there were a ton of them in the level. Diablo 3 had its own version of the cow level called Whimsyshire, which features colorful teddy bears in a rainbow-filled level, the complete opposite of the rest of Diablo 3.