What is a Pet Door?

Mary McMahon
Mary McMahon

A pet door is a small door designed to allow dogs and cats to move between indoors and outdoors without bothering their owners. A number of designs are on the market for animals of various sizes and owners of different needs. Generally, a model for cats is known as a “cat flap,” while a version designed for dogs is called a “doggie door.” A pet door can be highly useful, and also extremely technologically sophisticated.

Cats and dogs.
Cats and dogs.

A basic pet door consists of a small hole cut into a door or window at the pet's level. A flap is mounted in the door, allowing animals to pass in and out of it. Often, the flap is anchored with a magnet, so that it will not blow open in the wind. Many pet doors also lock, so that owners can keep animals inside when they need to. A more sophisticated pet door might only go one way, allowing animals to come in, but not to go out, for example. For pet owners who want to control the whereabouts of their animals, this can be very useful.

Raccoons can sometimes get in through pet doors.
Raccoons can sometimes get in through pet doors.

Even more technologically advanced pet doors link to radio collars on individual animals, allowing only a specific cat or dog into the house. This is useful in a neighborhood with many animals, to ensure that no unwanted visitors come in through the pet door. In regions with pests such as raccoons and skunks which could potentially invade, a controlled access pet door is crucial.

Since a determined thief could potentially use a pet door as an access point, most pet doors are designed to prevent human access. In general, a pet door is too small for a person to fit through. Most pet owners also lock their pet doors when they go on trips, to ensure that no one can take advantage of an empty house. Pet doors which use radio collars or similar technology are also useful for preventing unwanted human visitors in addition to the animal pests they are intended to deter.

Although many pet doors are designed to be fitted into an existing door, some companies have versions which do not require major home construction. For people who rent their homes, this is very important, as pet owners do not want to replace their doors every time they move. Some pet doors are designed to fit as an extra panel into a sliding glass door, for example, or can be fitted into a window frame. These pet doors can be taken along with the pet owners to a new home, allowing for years of potential use.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Is there any risk of wild animals coming into my house through a pet door? I feel like I have heard stories of racoons and possums coming into people's homes through a pet door flap.

Maybe these are just urban legends though. I would like to get one for my cat but I don't want to have to deal with any new "pets."


One thing to consider when you are buying a pet door is whether or not you want to get an insulated one. The insulated pet doors cost a little bit more money but they might be worth it to avoid a cold draft in the winter.

I had a friend who had a pet dog door that was not insulated and her kitchen was always freezing in the winter time. I decided then that if I ever had a pet door I would have to get an insulated one.


I had a cat door installed when I moved into my new house because we had one at the old house and both me and my cat had grown used to it. My little cat Shelly spends most of her day outside but she comes in at night to sleep.

One thing I really like is that my new cat door has a feature to lock it so if I don't want Shelly to get out I can keep her in. Sometimes there are dogs or workers around and I would rather she stayed away.

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