CSS aspect ratio and some everyday uses for it

CSS aspect-ratio has been working in browser for a couple of years now and I want to share some ways that I frequently utilize it in my day to day work.

2022 new CSS hotness series

This is article is a part of a series I'm going to be doing talking about some of the cool new things that have come to CSS in the last couple of years.

  1. Fluid type and sizing using clamp(), min(), max()
  2. where(), is(), has()
  3. aspect-ratio (You are here)
  4. Container Queries

Image sizing

I most often find myself reaching for aspect-ratio to size images in combination with object-fit. It can be useful to keep images sized similarly between different items in a grid of content (at least until subgrid works everywhere).

Example of a figure/caption

In this example I have a figure and caption. The figure is using a grid layout that limits the width of the image and then the image has an aspect-ratio of 1 which will keep is square.

Video sizing

Another frequent use I find for aspect-ratio is to make videos embeds (specifically iframes from viemo/youtube) responsive. This requires fairly minimal CSS. You need to set the width and height to 100%, then set the aspect-ratio to match the video (in this case 16 by 9), and then object-fit: contain, this will keep the image the correct ratio and allow it to resize.

.responsive-video {
width: 100%;
height: 100%;
aspect-ratio: 16 / 9;
object-fit: contain;

Example of a responsive video

I've got a longer post on just responsive videos and some history on how they used to be done.