Tagged “aspectratio”

I’m wary of list-based clickbait – and Adam’s recent 6 CSS snippets every front-end developer should know in 2023 feels like that – however I like this modern and minimal approach to creating a circle. I’ve previously seen aspect-ratio: 1 used to create a square box and it’s a lovely shorthand for “make width and height equal”. It makes sense that you can use it for a circle too, just by adding some border-radius.

.circle { inline-size: 25ch; aspect-ratio: 1; border-radius: 50%; }

Recently I’ve noticed some developers recommending using the CSS aspect-ratio property directly on images. My understanding of aspect-ratio was that it’s not so much intended for elements like img which already have an intrinsic aspect ratio, but rather for the likes of div which do not. Furthermore, when the goal is to prevent the layout shift that can occur after an image loads we should supply our images with width and height HTML attributes rather than using CSS.

In this timely post, Jake helpfully explains how width and height attributes are used by CSS as presentation hints to automatically set an aspect-ratio that will also, in cases where the attributes were set wrongly, fall back to the image’s intrinsic aspect ratio. Therefore, concentrating on HTML alone is ideal for our content images. My previous approach seems sound but I now know a little more about why.

If I'm adding an image to an article on my blog, that's content. I want the reserved space to be the aspect ratio of the content. If I get the width and height attributes wrong, I'd rather the correct values were used from the content image. Therefore, width and height attributes feel like the best fit. This means I can just author content, I don't need to dip into inline styles.

If it's a design requirement that the layout of an image is a particular aspect ratio, enforcing that with aspect-ratio in CSS can be appropriate. For example, a hero image that must be 16 / 9 – if the image isn't quite 16 / 9 I don't want it messing up my design, I want the design to take priority. Although, if the image isn't actually that aspect ratio, it'll either end up stretched (object-fit: fill), letter-boxed (object-fit: contain), or cropped (object-fit: cover). None of which are ideal.

Chris Coyier takes the new CSS aspect-ratio property for a spin and tests how it works in different scenarios.

Note that he’s applying it here to elements which do not have an intrinsic aspect-ratio. So, think a container element (div or whatever is appropriate) rather than an img. This is line with a Jen’s Simmons’ recent replies to me when I asked her whether or not we should apply aspect-ratio to an img after she announced support for aspect-ratio in Safari Technical Preview 118.

A couple of interesting points I took from Chris’s article:

• this simple new means of declaring aspect-ratio should soon hopefully supersede all the previous DIY techniques;
• if you apply a CSS aspect-ratio to an element which has no explicit width set, we still get the effect because the element’s auto (rendered) width is used, then by combining that with the CSS aspect-ratio the browser can calculate the required height, then apply that height;
• if the content would break out of the target aspect-ratio box, then the element will expand to accommodate the content (which is nice). If you ever need to override this you can by applying min-height: 0;
• if the element has either a height or a width set, the other of the two is calculated from the aspect ratio;
• if the element has both a height and width set, aspect-ratio is ignored.

Regarding browser support: at the time of writing aspect-ratio is supported in Chrome and Edge (but not IE), is coming in Firefox and Safari, but as yet there’s no word regarding mobile. So I’d want to use it as a progressive enhancement rather than for something mission critical.