Ristretto is a type of espresso coffee that is more concentrated and flavorful than a regular espresso shot. It is made with the same amount of ground coffee as a regular espresso shot, but extracted with a finer grind using half as much water. The resulting shot is shorter, usually around 20 ml, and contains more of the flavor compounds that dissolve most quickly from coffee grounds. Ristretto shots are less bitter and exhibit a more intense "espresso" character than regular espresso shots.

The word "ristretto" means "restricted" in Italian, and refers to the small volume of water and short extraction time used to make the shot. Extraction is generally stopped at around 15 seconds, instead of the 25 to 30 seconds used for a regular espresso shot. This shorter extraction time means that a ristretto contains fewer chemical compounds overall than a longer extraction, leading to a different balance of tastes and aromas.

Ristretto shots are the base for some coffee drinks, such as the Flat White and Holiday Spice Flat White, and can be requested in any espresso-based beverage. They are usually served without any added milk or sweeteners, but can be diluted into a cup of water or milk to make other coffee drinks.

In summary, ristretto is a type of espresso coffee that is more concentrated and flavorful than a regular espresso shot. It is made with the same amount of ground coffee, but extracted with a finer grind using half as much water, resulting in a shorter shot with a sweeter, richer flavor.