Day 80: container style queries

posted on

It’s time to get me up to speed with modern CSS. There’s so much new in CSS that I know too little about. To change that I’ve started #100DaysOfMoreOrLessModernCSS. Why more or less modern CSS? Because some topics will be about cutting-edge features, while other stuff has been around for quite a while already, but I just have little to no experience with it.

Container style queries allow querying the computed values of a query container.

No browser supports it yet, but we should be able to do something like this:

.card {
  aspect-ratio: 1 / 1;

.card--wide {
  aspect-ratio: 16 / 9

@container style(aspect-ratio: 16 / 9) {
  img {
    object-fit: cover;

We can check whether a container has a specific property and value assigned and apply additional styles based on this condition. Chrome support container style queries behind a flag, but only with custom properties, not ordinary properties.

Here’s an example based on a component I've built a while ago where this can be useful. We have a card component that can be used in different ways. It can contain just text, text and an image, text and a video, and also text with a background color. Most background colors in our design system work well with black as the text color, but there’s one exception.

:root {
  --nebelgrau: #d6d1ca;
  --flieder: #aaaafa;
  --abendstimmung: #49274b;

.card {
  --bg: var(--nebelgrau);
  background-color: var(--bg);
<div class="card">
  <h2>Chapter 1</h2>

<div class="card" style="--bg: var(--flieder)">
  <h2>Chapter 2</h2>

<div class="card" style="--bg: var(--abendstimmung)">
  <h2>Chapter 3</h2>

Chapter 1

Chapter 2

Chapter 3

I could assign a class to this specific card variation and just change the text color. That’s actually what we’re doing at the moment, but with style queries I can create a general rule that changes the text color whenever the container has a specific background color.

@container style(--bg: var(--abendstimmung)) {
  * {
    color: #fff;
Note: The color is probably still black for you, but it's white in supported browsers (Only Chrome behind a flag at the moment.)

Chapter 2

See on CodePen

Further reading

Do you want to learn even more awesome CSS?

I'm running a workshop with my friends at Smashing Magazine in which I introduce you to the most useful modern features in CSS and show how you can implement them today in your code base to improve scalability, maintainability, and productivity.

Learn more about the workshop!

Overview: 100 Days Of More Or Less Modern CSS