A deep-fat fryer — the same appliance called a deep fryer — is the dedicated vessel for deep-frying, built to hold a large volume of oil at a steady high temperature. Domestic versions are small countertop boxes with a basket and thermostat; commercial fryers are heavy-duty stainless-steel tanks, often in battery formation, with powerful burners or elements, filtration systems, and precise thermostatic control. The design solves frying’s central problem: when cold food hits the oil, the temperature must recover fast, or the food absorbs grease instead of crisping. Good fryers therefore combine thermal mass, fast heat recovery, and a cool zone beneath the elements where fallen crumbs settle instead of burning. In foodservice the fryer is a profit engine — chips, chicken, and battered fish — and also a safety focus, since hot oil demands strict discipline and filtration extends oil life.