What Is a Pet Microchip and How Does It Work?

A pet microchip is a passive radio-frequency identification (RFID) transponder encased in a biocompatible glass capsule roughly the size of a grain of rice (approximately 12mm long, 2mm in diameter). "Passive" means the chip contains no battery and requires no internal power source — it remains completely inert until activated by an external scanner.

When a microchip scanner is passed over the animal at close range, it emits a low-power radio frequency that energizes the chip momentarily. The chip responds by transmitting its unique identification number to the scanner's display. This number — a 15-digit code conforming to the ISO 11784/11785 standard — corresponds to a database record containing the owner's contact information.

The chip itself contains only the number. All identifying information (owner name, address, phone, veterinarian) is held in a pet registry database, which is why database registration is as critical as the implantation itself.

The Implantation Procedure: What to Expect

Microchip implantation is a straightforward outpatient procedure performed without sedation in most cases. The chip is pre-loaded in a sterile hypodermic needle slightly larger than a standard vaccine needle. In dogs and cats, the standard implantation site is the subcutaneous tissue (the loose skin) between the shoulder blades.

The procedure takes approximately 10–30 seconds. Most animals react similarly to a standard vaccination — a brief moment of discomfort. Some younger animals or particularly sensitive individuals may be momentarily startled, but the vast majority show no adverse reaction. Once implanted, the chip is anchored by the surrounding tissue within a few weeks and rarely migrates significantly from the implantation site.

After implantation, your veterinarian should scan the chip immediately to confirm it reads correctly and the number matches the chip documentation. Retain this documentation carefully — it contains the chip number you'll use to register with a database.

Cost: An Affordable Investment

Microchipping is one of the most cost-effective interventions in pet ownership. The procedure typically costs between €15–€60 at a veterinary clinic, depending on your location and whether it's performed as part of a puppy/kitten wellness visit bundle or as a standalone procedure. Some animal shelters and rescue organizations offer microchipping events at reduced cost (€10–€20) or free of charge.

Database registration is typically a one-time fee of €10–€25 with reputable national registries. Unlike a collar tag, a microchip requires no ongoing purchase or replacement — one implantation for a lifetime of identification. The only ongoing requirement is keeping your contact information updated in the registry when you move or change phone numbers — a step many owners forget and that renders the chip effectively useless.

Why Collar Tags Alone Are Not Enough

Collar ID tags are the first line of identification and absolutely still recommended — they allow any member of the public to immediately identify and contact you without needing a scanner. However, collars and tags have significant limitations: they can fall off, be removed (intentionally or accidentally), become unreadable through wear, or be incompatible with microchip-free pets found without collars.

A microchip provides permanent, tamper-resistant identification that cannot be accidentally lost. This is particularly valuable if your pet is stolen — a chip provides evidence of ownership that a tag cannot. Microchips are also required for international travel and as proof of rabies vaccination compliance in many jurisdictions. The combination of both collar tag and microchip provides the most comprehensive identification coverage.

The Importance of Registry Registration

This is the step most commonly missed. A microchip without registration is like a phone without a phone book entry — the number exists but leads nowhere. After implantation, immediately register your pet's chip number with a national or international pet registry. In Spain, registration with REIAC (Registro Español de Identificación Animal) is legally required. In the UK, registration with a database approved by Defra is mandatory. Keep your registration current — update your address and phone number any time they change. When you adopt from a shelter, verify that the chip number has been transferred to your name in the database.

Statistics on Return Rates

Research consistently demonstrates the life-saving impact of microchipping. A landmark study of 53 animal shelters in the United States found that microchipped dogs were returned to their owners 52.2% of the time, compared to just 21.9% for non-microchipped dogs. For cats — who are far less commonly microchipped — the difference was even more dramatic: 38.5% return rate for microchipped cats versus a mere 1.8% for non-chipped cats. When microchipped pets were not reunited with their owners, the most common reason was incorrect or outdated registry information — not chip failure.

International Travel Requirements

For travel between countries, particularly into the European Union, a microchip conforming to the ISO 15-digit standard is mandatory for all dogs, cats, and ferrets. The chip must be implanted before or on the same day as the rabies vaccination to be valid for EU pet passport purposes. Some countries additionally require proof of antibody titers (blood tests confirming rabies vaccine efficacy), which must be performed at least 30 days after vaccination. For travel outside the EU, always check the specific entry requirements of your destination country months in advance — requirements for Australia, New Zealand, Japan, and the UK are particularly stringent.