How to read a pet's microchip number (and what to do with it)

A pet microchip is a small glass capsule with a passive transponder, implanted under the skin between the shoulder blades. It has no battery and cannot be tracked like a phone — it can only be read by a scanner.

The number

• ISO chips have 15 digits, starting with a country prefix: 248 for Serbia, 219 for Croatia
• Older US-style chips (11-digit AID format) are not ISO and are not readable in the EU — if you adopted an older imported pet, ask a vet whether a new ISO chip is needed

What the number does

The chip itself stores nothing about you. It identifies the animal; a scanner reading it gives you the number, and you (or a vet, or a shelter) type that number into a register to see the owner's contact details.

Two things to do if you adopt or buy a pet

1. Get the chip read and the number written down on the pet's records

2. Make sure the register entry has your current phone number and address — the most common reason lost pets never come home is a stale contact in the register