A cat slips out of an open door and doesn’t come back. Three streets away, someone finds it and takes it to a vet. The vet waves a scanner over its shoulders, a number comes up, and by evening the cat is home.
That only happens if the cat has a microchip, and if the details behind the chip are right. The second part is where it usually goes wrong.
The short version
- A microchip is a tiny tag under the skin, about the size of a grain of rice.
- Putting it in takes seconds and feels much like a jab.
- It holds one number. Your name and phone are in a database linked to it.
- Moved or changed number? Update the database yourself. This is the most common failure.
- If your cat wears a collar too, make it a quick-release one.
What a microchip is
A microchip is a small tag, roughly the size of a grain of rice, that sits under the skin between the shoulder blades. It holds a single unique number. When a vet or rescue passes a scanner over it, that number shows up.
The number on its own means nothing. It has to be registered in a microchip database, along with your name, address and phone number. That record is what gets a cat home.
A chip isn’t a tracker. It has no battery and no GPS, so it can’t tell you where your cat is. It only works once someone has found the cat and scanned it.
Does it hurt?
A vet or a trained person puts the chip in with a needle, much like a vaccination. PDSA says it’s quick and fairly painless and takes a few seconds, and that cats very rarely react. Many cats are chipped while they’re asleep for neutering, so they never notice.
International Cat Care agrees with the world’s vet bodies that chipping is safe and very rarely causes problems. Once in, the chip lasts for life.
Why it works
A large study in the United States looked at more than 7,700 chipped animals arriving at 53 shelters. Chipped cats went home about 20 times more often than stray cats in general. Without a chip, a lost cat looks just like any other cat.
The most common failure: old details
In the same study, when the shelter couldn’t find the owner of a chipped animal, the top reason was a wrong or disconnected phone number. Some chips had never been registered at all.
- Check it’s registered. Ask your vet for the chip number and look it up, or ask the database to confirm your details.
- Update it when you move. Your vet can find the chip number for you, but International Cat Care says the update itself is done with the database company, usually online. Don’t assume the vet has passed it on.
- New phone number? Same again.
- Adopted a cat? Make sure the chip is moved into your name. A good rescue will do it for you.
Collars: quick-release only
A collar with a tag helps neighbours see a cat has a home. But collars come off, and the wrong one can hurt. Cats Protection warns that a cat’s leg or jaw can get caught in an elasticated or loose collar.
- Choose a quick-release collar that snaps open if it catches on something.
- Fit it so two fingers slide underneath.
- Treat it as an extra, never instead of a chip.
Chips have one more use. Some cat flaps read them, and only open for your own cat, which keeps the neighbour’s cat out of your kitchen.
Where it’s the law
England. Since 10 June 2024, owned cats must be chipped before they’re 20 weeks old, with the owner’s details kept up to date in an approved database. Owners can be fined up to £500. Community cats that live with little human contact aren’t covered.
The European Union. Any cat travelling between EU countries already needs a microchip, a rabies vaccination and a pet passport. In April 2026 the EU also agreed its first rules on the welfare of cats and dogs, which say every cat must be chipped and registered in a national database, pet cats included. The rules come in step by step over the next few years.
Cyprus. Cyprus has required chips for dogs since 2002, but not, so far, for cats. The new EU rules will change that, and the main duties are expected from 2028. A proposal to chip street cats neutered under the island’s programme is also being discussed.
Wherever you live, rules change. Your vet will know what applies to you.
Found a cat? Get it scanned
A friendly cat that suddenly turns up at your door may be someone’s lost pet. If it’s safe to carry it, take it to a vet to be scanned. In the UK, PDSA says this is always free. Elsewhere, phone the vet and ask first. Rescues and some volunteers have scanners too.
No chip doesn’t mean no owner. Our guide to finding a street cat covers the next steps, and you can make a lost or found cat poster in a minute.
Questions people ask
Does microchipping hurt a cat?
It feels much like a vaccination and takes a few seconds. Most cats barely react, and many are chipped while asleep for neutering.
Can a microchip track my cat?
No. A chip has no battery or GPS. It holds a number that a scanner reads once someone has found your cat.
Why didn’t the chip get my cat home?
Usually because the details in the database were out of date, or the chip was never registered. Update the database yourself whenever you move or change your phone number.
This guide is general information, not veterinary or legal advice. Rules differ by country, and your vet can tell you what applies where you live.
A chip gets a lost cat home. A photo helps people know it when they see it. Snap your cat and add it to your CatDex.
