A microchip flap opens only for the numbers you have registered, which stops the neighbor’s cat entering — it cannot stop a determined cat that follows yours through on the same swing.
Selective entry is the whole reason this category exists, and it works — with one gap.
What it does
Reads the chip or tag, unlocks, and stays locked for everything else. Up to 40 animals can be registered on some models, 25 on others.
The gap
Tailgating. A confident cat waiting outside can follow yours through before the flap closes. No flap on the market prevents this entirely; a curfew that keeps your cat in overnight reduces the opportunities.
The other direction
Several flaps also control exit, which is how you keep a cat in before a vet appointment without shutting the whole house.
If a strange cat has already learned the flap
Lock it for two weeks, feed indoors, and let the intruder lose the habit before returning to normal operation.
This does not replace your device’s manual. Blade temperatures, locking mechanisms and cleaning procedures differ from model to model, and the manufacturer’s instructions take precedence over anything written here. Unplug a device before dismantling it, check a hot blade or an air nozzle against your own hand before it goes anywhere near an animal, and keep a mechanism that closes or rotates under supervision until you know how it behaves.
Last reviewed 2026-08-17