If your pet gets lost, the identification you chose before it happened decides how quickly they come home. This guide summarises what the American Veterinary Medical Association (AVMA) says about microchips and collars, and what to ask about any tracker you consider. It covers US advice. For Great Britain, see our guide to dog ID tags and microchips and the law. This is general information, not veterinary advice.

This guide is based on the public source listed below. We have not tested any microchip, tag or tracker.

What the AVMA says

Source: AVMA, "Microchips reunite pets with families" (the page shows no date; read in a browser). Last checked: 17 October 2026.

  • What a microchip is. A tiny electronic device about the size of a large grain of rice, implanted just beneath the skin with a preloaded syringe. The AVMA says most pets feel only brief discomfort, similar to a routine vaccination.
  • How it works. Each chip holds a unique identification number. It has no internal power source, so it stays inactive until a compatible scanner passes over it. The scanner shows the number, which can be used to identify the owner, provided the owner's contact details are up to date. In the US the chip is typically placed between the shoulder blades.
  • It is not a tracker. The chip contains only an ID number: it cannot show where a pet is.
  • Registration is the key. A microchip is only as effective as the information linked to it. If the registry details are incomplete or outdated, a lost pet might not be returned even after the chip is scanned. The AVMA points to a lookup tool from the American Animal Hospital Association and suggests asking your vet to scan the chip at routine check-ups. August 15 is Check the Chip Day.
  • Which type. There is no single US standard, but the AVMA and many other organisations support chips that meet ISO standards: a 15-digit number at 134.2 kHz, which helps pets that travel internationally.
  • Still wear a collar. The AVMA says it is best for microchipped pets to wear a collar with current identification, such as a license tag, a rabies tag and a personalised ID tag.

If you consider a GPS tracker

The AVMA page we read does not cover trackers, so we give no advice on them beyond these questions to ask the seller:

  1. What does it need to work, such as a subscription, mobile coverage or a charger, and what happens if you stop paying?
  2. How long does the battery last, and how is it charged?
  3. Does it replace a microchip or tag? The AVMA says it is best to keep a collar with ID, and a microchip stays registered either way.
  4. Size and weight for your pet, the return policy and who pays for returns.

What we could not confirm

  • How accurate or reliable any tracker is, costs and rules outside the US.

Source: AVMA, microchips reunite pets with families.