Cortar means to cut. A cortado is an espresso cut with an equal quantity of warm milk — enough to take the edge off the acidity and nothing like enough to make it a milk drink.
It is served in a small glass, usually around 110 ml, and it is drunk quickly.
The proportions
Roughly one to one. A double espresso of 36 g with 40 to 60 ml of milk. The milk is steamed to about 60 °C and barely textured — you want it silky, not foamy.
That is what separates it from every other milk drink: there is almost no foam, and the coffee is still unmistakably the point.
Why the glass matters
Traditionally a vaso, a small thick glass, sometimes with a metal handle. Glass shows the two layers before you stir, which is part of the pleasure, and the small volume keeps the drink hot to the last mouthful.
Around Spain and beyond
In the Basque Country it is often a ebaki. In Portugal, a pingado is close. In Cuba and Miami, a cortadito adds sugar, often whipped into the first drops of espresso.
Australia’s piccolo latte is a cousin — a ristretto in a small glass topped with textured milk — and is milkier than a true cortado.
Making one
Pull a double, texture 60 ml of milk with a very short stretch and a long spin, and pour it straight in. There is no latte art here; the surface is glossy and plain.
Because there is so little milk, the espresso has nowhere to hide. A cortado made with a badly extracted shot is unpleasant in a way a latte would have concealed.
Questions people actually ask
How is it different from a flat white?
Volume and ratio. A cortado is about 1:1 espresso to milk in a small glass; a flat white is roughly 1:3 in a 150 to 175 ml cup. The cortado is considerably more coffee-forward.
Should a cortado have foam?
Very little. The milk is warmed and lightly textured to cut the acidity, not foamed. A thick foam cap makes it a small cappuccino, which is a different drink.