A microchip implant is an identifying integrated circuit placed under the skin of a dog, cat, or other animal. The chips are about the size of a large grain of rice and are based on a passive RFID technology. Microchipping dogs and other animals that are outdoors a lot is especially important and can help in ownership disputes if a dog gets lost.

Tattooing is another, older method for identifying animals. Tattoos can be difficult to find and won’t even be looked for on most pets. Once the fur grows back over the tatoo it isn’t easy to find.

Radio-frequency identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders.

An RFID tag is an object that can be stuck on or incorporated into a product, animal, or person for the purpose of identification using radiowaves. Some tags can be read from several meters away and beyond the line of sight of the reader.

Most RFID tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating a (RF) signal and can also be used for other specialized functions. The second is an antenna for receiving and transmitting the signal.