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A lot of cat owners have windows that lead to a balcony, garden, patio, or another area that a cat may enjoy. The biggest issue here is that cats can get really annoying with their demands to go out, then in, then out again and so on.
The best solution both for the cat owner and the cat is to get a cat door. But normally cat doors are designed for walls so finding a cat door for vertical window requires some effort.
Here you will find the most comprehensive guide for choosing and installing a cat door for glass, I’ve spent hours researching online for the best options.
I’ve checked numerous forums, products and customer reviews and I’ve compiled the best collection of window cat doors. So check it out, this is the best resource online on this topic – IMHO.
Why is this subject so interesting to me? Well, I have a cat that drives me CRAZY in cold weather, when I have to keep my balcony window doors closed so this makes it kinda personal for me 🙂
Can You Put A Cat Door In A Window?
For a long time, I was not aware that you can actually install a cat door in the window. But yes, it is possible, you just need the right cat door for it. This simply means that when buying one be sure that the cat door specifications mention that it can be installed in a window.
You also need to take into consideration if your window is single glazed (single pane of glass) or double glazed as it will make a difference in the installation.
If you want cat flap in a double glazed window then if the space in between is filled with gas then you will need a new unit with a hole pre-cut in it, so beware of this.
Many people have built/bought a completely new window glass with a hole for the cat door and kept the old one as a reserve.
Installing a cat door in window is a bit more delicate that installing a cat door in wall but it is doable and the peace you’ll gain by doing so is very much worth the effort.
Microchip Cat Door For Window

I’ve already made a post about this great cat flap for windows if you want to read the whole review. Below I will highlight the main points of this cat door specifically when using it for the window.
The Process Of Installing This Window Cat Flap
- First of all, you need to program the cat door prior to the installation as this is the best practice (check my full review on this).
- A circular hole (212 mm in diameter) needs to be cut in the window. As I’ve already advised this is best done by a professional but if you are a crafty person you can do it yourself – but only if you have a single pane of glass otherwise you will lose the insulation filling in a multi-glassed window. The start of hole needs to be in the level of your cat’s belly to be comfortable for it to pass through.
- The height is calculated as the starting point of the hole + 56 mm – in case you need to give these measures to your glazier
- For double or triple glass window make sure the space extender is non-metallic as metal can interfere with the microchip functionality of the door
- Beware that the Sureflap writing needs to be on the inside
- You will need a mounting adapter – 2 adapter pieces are included in a single box
- For the rest of the installation check the video below, this part is best seen in practice
Not to forget to mention: my research also showed that this is the best raccoon resistant cat door, in case this is one of your concerns.
For big cats: there is another version of this cat flap which is for bigger cats and selective entry only (the door is not dual scan from both sides), you can read my full review on this kitty door for window.
For those on a budget (that still want quality cat door): you can get this same cat door (smaller than the pet door version from above) with selective entry only (the door is not dual scan from both sides), it’s a bit cheaper because of the cut functionality, check it on this link.
This is truly a perfect cat door for glass french door / window, it completely integrates into the glass and provides a very practical solution for the problem of cats going in and out all the time.
Transparent Cat Door In Window

This transparent cat flap will fit perfectly in any type of window and the best part is that you will still keep your view. Having an unobstructed view is especially important for cat owners with a small apartment (like me) where every little space counts.
- Suitable for all cats, even big ones as the size is: 7.25” x 8”
- Your cat does need not to be chipped as the door is manually operated
- There are 4 ways to control the access: fully locked, fully unlocked, in only, out only – which is enough for the needs of a normal, healthy cat
- This glass cat door is not automated but it is with a reasonable price and you will still get the basic benefits of a having a cat door PLUS you’ll keep your view – which is not for underestimation
- Made from weather-resistant, durable, long-lasting material that is unbreakable: built from UV stable 100% polycarbonate
- One quiet cat flap: only cat owners with shy cats will understand how important this is, the cat will not be stressed going through the cat door as the edges are wrapped in a brush strip which guarantees silent opening of the cat flap
- It is not airtight so not suitable for cold weather areas, although some people were able to make satisfying adjustments
Installation
There is a picture of 4 steps required to install this window cat flap, it is shown on the product page one scroll below and you’ll also receive directions in the package.
The hardest part of course is cutting the hole in the glass. In my opinion, this part is best done by a professional glazier but there are youtube videos online that teach you how to cut a hole with a circular glass cutter. If you decide to diy please be careful and use gloves when working with cut glass.
The package includes screws so you’re all set with them.
If you have a window or a glass door leading to an outside litter box this glass fitting cat door will save you from the constant need to let your cat in and out, and this is particularly important for a good night’s sleep. I mean we all know how cats get crazy at night and have weird wishes and energy outbursts.
This glass cat flap has the best window integration I’ve seen so far so it’s definitely worth checking it out.
Glass Fitting Cat Flap

This is one simple but functional cat door for a vertical window. It operates manually and it is mainly for those that don’t want to get too involved in electronics and just need a basic cat door that will still do the job.
The design is cute and I particularly like the writing “Cat Mate”, it just feels kinda warm 🙂 (although I know it’s a brand name it still makes me feel good when I see it).
- Very easy to use
- The cat flap is lined with a draft and weatherproof brush
- Silent opening and closing (because of the brush) – your cat will have no fear going in and out
- Manual rotary lock in 4 ways: fully locked, fully unlocked, in only, out only
- Strong lock to prevent another animal intrusion
- The cat flap is made of tinted plastic and is transparent for allowing your cat to see trough
- Easy installation
- Affordable
- Very simple and basic cat flap (although this is not negative – just to emphasize it)
The best indicator of the quality of this door is the 3-year guarantee provided by the manufacturer – you will definitely get your money’s worth.
The Most Advanced Version: Remote Control Cat Door / App Controlled Cat Door

And I have to share with you the funniest video of cats learning to use a cat flap – it is hilarious 😀