CSS Aspect Ratio it's finally here

#css

If you're a front-end developer, you must have looked up "CSS Aspect Ratio" more than once.

One of these things one would expect to be existing in CSS for a long time, but it was not! (Well, not really)

There are some hacks to achieve it.

But not a proper aspect-ratio solution, until now that is!

Chrome just got support for the aspect-ratio property.

To give you an example of how it works:

Using the CSS aspect-ratio

The syntax for the aspect-ratio is pretty simple.

aspect-ratio: width / height;

Alternatively you have some CSS basics like:

aspect-ratio: inherit;
aspect-ratio: initial;
aspect-ratio: unset;

To test it out, let's make a resizable box to test out how it will work.

<div class="container"></div>

Inside of the container, we will place two boxes that will have their own aspect ratio's

Box 1 will have an aspect ratio of 1/1
And Box 2 will have a 16/9 aspect ratio.

<div class="container">
  <div class="box box1"></div>
  <div class="box box2"></div>
</div>

First, we'll start by styling the container. We want it to wrap the elements inside but add the CSS Resize property.

.container {
  display: flex;
  gap: 16px;
  resize: horizontal;
  overflow: auto;
}

Then we can move to our generic box styling. This will be the styling that each box will get.

.box {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: #fff;
}

As you can see, this is mainly used to center the content inside the boxes and give them a bigger font.

Now onto the magic part 🪄.

CSS square aspect-ratio 1/1

For our first box, we will use a square aspect ratio. We can achieve this by using the following CSS.

.box1 {
  aspect-ratio: 1 / 1;
  background: #06d6a0;
  flex: 1;
}

This will provide us a square box that can grow in size.

CSS rectangle aspect-ratio 16/9

The second box will have a 16/9 aspect-ratio, which we can achieve by the following CSS.

.box2 {
  aspect-ratio: 16 / 9;
  background: #ef476f;
  flex: 1 0 auto;
}

Now we get the following result as you can test out in this Codepen.

Note: Browser support is not big, so you might not see it behave as expected. I've added the GIF, in the beginning to showcase how it works.

Browser Support

It's still very early days for the aspect-ratio browser-support. Chrome shipped it in production in version 88, and Firefox has it in beta, so you can enable it in Firefox.

Thank you for reading, and let's connect!

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Top comments (4)

Alex Lohr • Feb 1 '21

Which is really great, because the CSS trick using padding to add the height as a percentage of the width will obviously only work if there is a width to work with - if for example you have a grid with a fixed height, you cannot set the width to the desired aspect ratio using the padding of a pseudo element.

The only other way I found to solve this was to use a gif/svg with the desired aspect ratio in the content-url with height set to 100% and width set to auto:

aspect-16to9-no-width:before {
  content: url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='9'%3F%3Csvg%3E");
  height: 100%;
  width: auto;
}