A pet microchip is a tiny transponder, about the size of a grain of rice, implanted under the skin between the shoulder blades. It holds a unique ID number that a shelter or vet can read with a scanner and look up in a registry to find the owner. A microchip is not a GPS tracker: it has no battery and cannot show where your pet is. It only works if the chip is registered with your current contact information.
Microchipping is inexpensive, quick and widely recommended by groups such as the AVMA and the ASPCA. This guide explains how chips work, what they cost and how to keep the registration up to date.
How a microchip works
- Implant. A vet or trained technician injects the chip under the skin with a needle, similar to a vaccine. No anesthesia is usually needed, although many are placed during spay or neuter surgery.
- Registration. The chip number is linked to your name and contact details in a registry database.
- Scanning. If your pet is found, a shelter or vet passes a scanner over the pet. The scanner reads the chip's ID number using radio waves.
- Lookup. The staff look up the number to find the registry, which contacts you or shares your details.
The chip itself contains only a number, not your personal information.
Microchip vs ID tag vs GPS tracker
| Microchip | ID tag | GPS tracker | |
|---|---|---|---|
| Permanent | Yes | No; can fall off | No; on a collar |
| Visible to finders | No; needs a scanner | Yes | No |
| Shows pet's location | No | No | Yes |
| Needs power | No | No | Yes; must be charged |
| Typical cost | One-time fee | Low | Device plus usually a subscription |
The best protection is a combination: an ID tag with your phone number so neighbors can call you directly, plus a registered microchip as a permanent backup.
How much does microchipping cost?
Microchipping typically costs about $25 to $75 at a vet clinic, and often less at shelter clinics or community events, where it may be free or around $10 to $25. Prices vary by region and provider. Most shelter and rescue adoption fees already include a microchip; see pet adoption fees explained.
Registration is often free with the chip, though some registries offer paid premium plans with extra features. A basic registration is what matters for reunions. Look for low-cost spay and neuter clinics and humane societies near you, which often offer low-cost chipping.
Registering and updating your chip
A chip that is not registered, or registered with an old phone number, often cannot reunite a pet with its owner. To keep it working:
- Find your pet's chip number on adoption papers or vet records, or ask your vet to scan it
- Register the chip with the manufacturer's registry or another registry if it is not already registered to you
- Update your phone number, email and address whenever they change
- Add a backup contact
- Ask your vet to scan the chip at annual checkups to confirm it still reads
If you do not know which registry holds a chip, the AAHA Universal Pet Microchip Lookup tool (petmicrochiplookup.org) searches participating registries by chip number.
Looking up a microchip on a found pet
If you find a pet, take it to any vet clinic, shelter or animal control office for a free scan. If staff find a chip number, they can look it up and contact the registry. As a finder, you usually will not receive the owner's personal details directly; the registry or shelter makes contact. See found a stray dog for the full process.
Common questions about safety
Microchips are generally considered safe. Possible problems, such as a chip moving from its original location, swelling at the site or a chip that stops reading, are uncommon. Tumors at the implant site have been reported but are considered very rare. Discuss any concerns with your vet.
Are microchips required by law?
Some states and cities require microchips for shelter animals before adoption, for dogs being licensed, or for certain breeds, and some require shelters to scan every animal they take in. Rules vary, so check your local ordinance.
Chips and international travel
The US uses several chip frequencies, while many countries require chips that meet the ISO 11784/11785 standard. If you plan to travel abroad with your pet, ask your vet whether your pet's chip meets the destination's requirements.
For what to do if your pet goes missing, see our lost pet checklist, and use the near me page to find shelters in your area.