A key programmer for cars is a device or tool used to program new or replacement keys to a vehicle. It syncs the car’s immobilizer system with the new key, allowing it to start the engine. These tools are essential when keys are lost, damaged, or additional keys are needed. Key programmers support various vehicle makes and models, depending on the device. Advanced models can program smart keys, fobs, and even reset immobilizer systems. They are commonly used by automotive locksmiths, dealerships, and professional technicians.