Container Queries: a Quick Start Guide

In the latest version of Chrome Canary, the most recent @container query proposal is available for use behind an experimental flag. Developed by OddBird’s own Miriam Suzanne, the draft builds upon the ideas previously proposed by other web standards experts like David Baron, who wrote the original draft.

Background

@Media queries sparked a responsive design revolution by allowing authors to change the style of elements based on the size of the entire viewport. Up until now, what could not be done was changing the style of an element based on the size of one of its nearest containers.

Syntax and an example

The proposed @container query syntax feels a lot like writing a @media query, but a main difference is that a @container query has to be implemented in two parts.

In this demo (which only works in the latest version of Chrome Canary), a blockquote is styled differently depending on the size of its container.

See the Pen Container Queries with Block Quotes by @dvdherron on CodePen.

Define a containment context

To achieve this, first define a containment context. This lets the browser know which container to query against later and how exactly to query that specific container.

article,
section {
  contain: layout size style;
}

The contain property is part of the existing CSS Containment Module. The layout value activates layout containment on the container, which ensures that “nothing outside can affect its internal layout, and vice versa.” Size also currently exists as a value for the contain property, and enables laying out a containment box without accounting for its descendants in either the inline or block axes. Style containment isolates counters that might exist inside of the container.

article,
section {
  contain: layout inline-size style;
}

With inline-size, a proposed change to the Containment Module, authors can be more specific when declaring in which dimension containment should be applied. (Block-size is also being considered as a containment type in the new proposal. Inline-size seemed to satisfy more use-cases, so is being developed first.)

Apply @-rules at desired breakpoints

Now that a containment context has been defined, the @container rule is used to tell the browser when and how styles should change inside each container.

With a narrow parent container, the blockquote features the image stacked on top of the text.

At the first breakpoint, the layout for the blockquote changes so that the profile image moves from being above the quote to sitting next to it, and the text describing the speaker gets a heavier weight applied.

/* change styles according to container size */
@container (min-width: 35em) {

  .quote {
    grid-gap: 1rem;
    grid-template: "media quote" auto/ max-content 1fr;
  }

  .media {
    align-items: center;
  }

  .source {
    font-weight: bold;
  }
}

At the second breakpoint, the size of the text for the quote and the attribution grows, the background changes color, and the overall shape of the blockquote changes by way of a clip-path.

@container (min-width: 60em) {

  .quote {
    --quote-size: 1.5rem;
    --quote-background: darkmagenta;
    clip-path: polygon(
      -0.04% 100.6%,
      1.12% -0.52%,
      95.65% 11.18%,
      96.46% 90.05%
    );
    padding: 1.25em 3em;
    max-width: unset;
  }

  .source {
    font-size: 1.1rem;
  }
}

Any styles inside of one of these @container blocks will be applied when the container fulfills the condition of the query.

Just as with @media queries, authors can write as many @container queries as needed.

All together now

With each blockquote sitting in a different sized container, they all look slightly different, at the same viewport size.

What’s next?

It’s still very early in the proposal process, so a lot regarding how container queries work could change.

• There might be a way to contain only the block axis.
• Queries could also be made against properties like aspect-ratio, orientation, or even custom properties and layout states.
• We already have viewport-relative units like vh and vw. Container-relative units could be on the horizon as well.

Bookmark Miriam’s scratch site for updates: Miriam’s CSS Sandbox.

To participate in discussions and implementation questions related to container queries, visit this project board: Open Issues & Work on the Contain 3 Spec.

Experiment and share

Follow these steps to get started experimenting and making your own demos:

• Download Chrome Canary or update to the latest version.
• Navigate to chrome://flags.
• Search for “CSS container queries” and select Enabled.
• Restart the browser.

The OddBird team would love to see what you come up with. Tag us on Twitter with a link to whatever you create. In the meantime, check out our collection of demos on CodePen for inspiration.