A rice cooker or rice steamer is a kitchen appliance used to automate and simplify the process of cooking rice. Traditionally, rice is cooked by measuring quantities of rice and water into a pot, bringing them to a boil on the stove, and then immediately lowering the temperature to a simmer. The rice cooker does the monitoring for you, simply measure the rice and water, and let it cook with a single press.
The rice cooker heats the water-rice mixture until all the water has either evaporated or is absorbed by the rice. This works on the principle that the boiling water maintains a constant temperature (212 °F or 100 °C at sea-level). Once the temperature changes, the device shuts off or switches to warm to keep the rice ready to serve. For consistent rice and easy cleanup, it is recommended to prepare at least 2 cups (dry), since some cookers will dry out or scorch rice at the bottom if they can't cool down fast enough.
Classic rice cookers introduced in the 1950s have a single switch with a "cook" and a "keep warm" mode, and they work without any internal computing. Newer models have programmable interfaces that add many features like delay timers, settings for different varieties of rice, and even settings for other foods.
Classic rice cookers include a steamer tray, and can be used for other foods including chicken, fish, and vegetables. Steaming can be done on its own, or while the rice cooks below. Creative cooks prepare grains other than rice by adjusting the amount of water added prior to cooking.
Settings available in programmable rice cookers commonly include, a white rice setting, a brown rice setting, a quick cooking setting, and a porridge setting, although different brands may include more or fewer options. These cookers can also be used to prepare risottos, pilafs, and rice puddings; however, most usually can not be used as steamers.
Rice cookers commonly come with a special cup to measure 180 ml, or about 6 oz of rice. It is important to note that a rice cooker that has water level markings on the side of the bowl will be for rice measured in this cup, not a standard measuring cup.
As the origin of the device, the rice cooker is considered an important part of modern Japanese cooking.