A key fob is a decorative item which many people carry with their keys, on a ring or a chain, often to provide a better grip or to simply make a personal statement. There is essentially no limit to the forms of key fobs available. Simple shapes of smooth metal or plastic, often with a message or symbol, are the most common. Some may be shaped into symbols or small representations of objects, or may be functional in themselves – small flashlights, calculators, penknives or other items are common. See keychain for a more extensive list of such items.

Electronic key fobs are used for remote locking motor vehicles. Early electric key fobs operated on infrared, so needed a clear line of sight, and could be copied using a programmable remote control. More recent models use Challenge-response authentication over radio, so are harder to copy and don't need line of sight to operate.