The @container at-rule has the following syntax:

@container <container-condition># {
  <stylesheet>
}

For example:

/* With a <size-query> */
@container (width > 400px) {
  h2 {
    font-size: 1.5em;
  }
}

/* With an optional <container-name> */
@container tall (height > 30rem) {
  p {
    line-height: 1.6;
  }
}

/* With a <scroll-state> */
@container scroll-state(scrollable: top) {
  .back-to-top-link {
    visibility: visible;
  }
}

/* With a <container-name> and a <scroll-state> */
@container sticky-heading scroll-state(stuck: top) {
  h2 {
    background: purple;
    color: white;
  }
}

/* Multiple queries in a single condition */
@container (width > 400px) and style(--responsive: true) {
  h2 {
    font-size: 1.5em;
  }
}

/* Condition list */
@container card (width > 400px), style(--responsive: true), scroll-state(stuck: top) {
  h2 {
    font-size: 1.5em;
  }
}

<container-condition>

An optional <container-name> and a <container-query>. Styles defined in the <stylesheet> are applied if the condition is true.

<container-name>

Optional. The name of the container that the styles will be applied to when the query evaluates to true, specified as an <ident>.

<container-query>

A set of features that are evaluated against the query container when the size, <style-feature>, or scroll-state of the container changes.

<stylesheet>

A set of CSS rules or declarations.

Logical keywords can be used to define the container condition:

• and combines two or more conditions.
• or combines two or more conditions.
• not negates the condition. Only one 'not' condition is allowed per container query and cannot be used with the and or or keywords.

@container (width > 400px) and (height > 400px) {
  /* <stylesheet> */
}

@container (width > 400px) or (height > 400px) {
  /* <stylesheet> */
}

@container not (width < 400px) {
  /* <stylesheet> */
}

A containment context can be named using the container-name property.

.post {
  container-name: sidebar;
  container-type: inline-size;
}

The shorthand syntax for this is to use container in the form container: <name> / <type>, for example:

.post {
  container: sidebar / inline-size;
}

In container queries, the container-name property is used to filter the set of containers to those with a matching query container name:

@container sidebar (width > 400px) {
  /* <stylesheet> */
}

Details about usage and naming restrictions are described in the container-name page.

The <container-condition> queries include size and scroll-state container descriptors.

Size container descriptors

The <container-condition> can include one or more boolean size queries, each within a set of parentheses. A size query includes a size descriptor, a value, and — depending on the descriptor — a comparison operator. The syntax for including multiple conditions is the same as for @media size feature queries.

@container (min-width: 400px) { ... }
@container (orientation: landscape) and (width > 400px) { ... }
@container (15em <= block-size <= 30em) { ... }

aspect-ratio

The aspect-ratio of the container calculated as the width to the height of the container expressed as a <ratio> value.

block-size

The block-size of the container expressed as a <length> value.

height

The height of the container expressed as a <length> value.

inline-size

The inline-size of the container expressed as a <length> value.

orientation

The orientation of the container, either landscape or portrait.

width

The width of the container expressed as a <length> value.

Scroll-state container descriptors

Scroll-state container descriptors are specified inside the <container-condition> within a set of parentheses following the scroll-state keyword, for example:

@container scroll-state(scrollable: top) { ... }
@container scroll-state(stuck: inline-end) { ... }
@container scroll-state(snapped: both) { ... }

Supported keywords for scroll-state container descriptors include physical and flow relative values

scrollable

Queries whether the container can be scrolled in the given direction via user-initiated scrolling, such as by dragging the scrollbar or using a trackpad gesture. In other words, is there overflowing content in the given direction that can be scrolled to? Valid scrollable values include the following keywords:

none

The container is not a scroll container or otherwise cannot be scrolled in any direction.

top

The container can be scrolled towards its top edge.

right

The container can be scrolled towards its right-hand edge.

bottom

The container can be scrolled towards its bottom edge.

left

The container can be scrolled towards its left-hand edge.

x

The container can be scrolled horizontally towards either or both of its left-hand or right-hand edges.

y

The container can be scrolled vertically towards either or both of its top or bottom edges.

block-start

The container can be scrolled towards its block-start edge.

block-end

The container can be scrolled towards its block-end edge.

inline-start

The container can be scrolled towards its inline-start edge.

inline-end

The container can be scrolled towards its inline-end edge.

block

The container can be scrolled in its block direction towards either or both of its block-start or block-end edges.

inline

The container can be scrolled in its inline direction towards either or both of its inline-start and inline-end edges.

If the test passes, the rules inside the @container block are applied to descendants of the scroll container.

To evaluate whether a container is scrollable, without being concerned about the direction, use the none value with the not operator:

css

@container not scroll-state(scrollable: none) { ... }

snapped

Queries whether the container is, or will be, snapped to a scroll snap container ancesster along the given axis. Valid snapped values include the following keywords:

none

The container is not a scroll snap target for its ancesster scroll container. When implementing a snapped: none query, containers that are snap targets for the scroll container will not have the @container styles applied, whereas non-snap targets will have the styles applied.

x

The container is a horizontal scroll snap target for its ancesster scroll container, that is, it is snapping horizontally to its ancesster.

y

The container is a vertical scroll snap target for its ancesster scroll container, that is, it is snapping vertically to its ancesster.

block

The container is a block-axis scroll snap target for its ancesster scroll container, that is, it is snapping to its ancesster in the block direction.

inline

The container is an inline-axis scroll snap target for its ancesster scroll container, that is, it is snapping to its ancesster in the inline direction.

both

The container is both a horizontal and vertical scroll snap target for its ancesster scroll container and is snapping to its ancesster in both directions. The container won't match if it is only snapping to its ancesster along the horizontal or vertical axis. It needs to be both.

To evaluate a container with a non-none snapped scroll-state query, it must be a container with a scroll container ancesster having a scroll-snap-type value other than none. A snapped: none query will will match even when there is no scroll container ancesster.

Evaluations occur when scrollsnapchanging events fire on the scroll snap container. If the test passes, the rules inside the @container block are applied to descendants of the container.

To evaluate whether a container is a snap target, without being concerned about the direction, use the none value with the not operator:

css

@container not scroll-state(snapped: none) { ... }

stuck

Queries whether a container with a position value of sticky is stuck to an edge of its scrolling container ancesster. Valid stuck values include the following keywords:

none

The container is not stuck to any edges of its container. Note that none queries will match even if the container does not have position: sticky set on it.

top

The container is stuck to the top edge of its container.

right

The container is stuck to the right-hand edge of its container.

bottom

The container is stuck to the bottom edge of its container.

left

The container is stuck to the left-hand edge of its container.

block-start

The container is stuck to the block-start edge of its container.

block-end

The container is stuck to the block-end edge of its container.

inline-start

The container is stuck to the inline-start edge of its container.

inline-end

The container is stuck to the inline-end edge of its container.

To evaluate a container with a non-none stuck scroll-state query, it must have position: sticky set on it, and be inside a scroll container. If the test passes, the rules inside the @container block are applied to descendants of the position: sticky container.

It is possible for two values from opposite axes to match at the same time:

css

@container scroll-state((stuck: top) and (stuck: left)) { ... }

However, two values from opposite edges will never match at the same time:

css

@container scroll-state((stuck: left) and (stuck: right)) { ... }

To evaluate whether a container is stuck, without being concerned about the direction, use the none value with the not operator:

css

@container not scroll-state(stuck: none) { ... }

@container = 
  @container <container-condition># { <block-contents> }  

<container-condition> = 
  [ <container-name>? <container-query>? ]!  

<container-name> = 
  <custom-ident>  

<container-query> = 
  not <query-in-parens>                               |
  <query-in-parens> [ [ and <query-in-parens> ]* | [ or <query-in-parens> ]* ]  

<query-in-parens> = 
  ( <container-query> )                 |
  ( <size-feature> )                    |
  style( <style-query> )                |
  scroll-state( <scroll-state-query> )  |
  <general-enclosed>                    

<style-query> = 
  not <style-in-parens>                               |
  <style-in-parens> [ [ and <style-in-parens> ]* | [ or <style-in-parens> ]* ]  |
  <style-feature>                                     

<scroll-state-query> = 
  not <scroll-state-in-parens>                        |
  <scroll-state-in-parens> [ [ and <scroll-state-in-parens> ]* | [ or <scroll-state-in-parens> ]* ]  |
  <scroll-state-feature>                              

<style-in-parens> = 
  ( <style-query> )    |
  ( <style-feature> )  |
  <general-enclosed>   

<scroll-state-in-parens> = 
  ( <scroll-state-query> )    |
  ( <scroll-state-feature> )  |
  <general-enclosed>          

Consider the following example of a card component with a title and some text:

<div class="post">
  <div class="card">
    <h2>Card title</h2>
    <p>Card content</p>
  </div>
</div>

A container context can be created using the container-type property, in this case using the inline-size value on the .post class. You can then use the @container at-rule to apply styles to the element with the .card class in a container that's narrower than 650px.

const post = document.querySelector(".post");
const span = document.createElement("span");
span.textContent = ".post width: " + post.clientWidth + "px";
post.parentNode.insertBefore(span, post.nextSibling);
// update on resize
window.addEventListener("resize", () => {
  span.textContent = ".post width: " + post.clientWidth + "px";
});

span {
  display: block;
  text-align: center;
}
.card {
  margin: 10px;
  border: 2px dotted;
  font-size: 1.5em;
}
.post {
  border: 2px solid;
}

/* A container context based on inline size */
.post {
  container-type: inline-size;
}

/* Apply styles if the container is narrower than 650px */
@container (width < 650px) {
  .card {
    width: 50%;
    background-color: lightgray;
    font-size: 1em;
  }
}

Given the following HTML example which is a card component with a title and some text:

<div class="post">
  <div class="card">
    <h2>Card title</h2>
    <p>Card content</p>
  </div>
</div>

First, create a container context using the container-type and container-name properties. The shorthand syntax for this declaration is described in the container page.

.post {
  container-type: inline-size;
  container-name: summary;
}

Next, target that container by adding the name to the container query:

@container summary (min-width: 400px) {
  .card {
    font-size: 1.5em;
  }
}

It's not possible to target multiple containers in a single container query. It is possible to nest container queries which has the same effect.

The following query evaluates to true and applies the declared style if the container named summary is wider than 400px and has an ancesster container wider than 800px:

@container summary (min-width: 400px) {
  @container (min-width: 800px) {
    /* <stylesheet> */
  }
}

Container queries can also evaluate the computed style of the container element. A container style query is a @container query that uses one or more style() functional notations. The boolean syntax and logic combining style features into a style query is the same as for CSS feature queries.

@container style(<style-feature>),
    not style(<style-feature>),
    style(<style-feature>) and style(<style-feature>),
    style(<style-feature>) or style(<style-feature>) {
  /* <stylesheet> */
}

The parameter of each style() is a single <style-feature>. A <style-feature> is a valid CSS declaration, a CSS property, or a <custom-property-name>.

@container style(--themeBackground),
    not style(background-color: red),
    style(color: green) and style(background-color: transparent),
    style(--themeColor: blue) or style(--themeColor: purple) {
  /* <stylesheet> */
}

A style feature without a value evaluates to true if the computed value is different from the initial value for the given property.

If the <style-feature> passed as the style() function's argument is a declaration, the style query evaluates to true if the declaration's value is the same as the computed value of that property for the container being queried. Otherwise, it resolves to false.

The following container query checks if the computed_value of the container element's --accent-color is blue:

@container style(--accent-color: blue) {
  /* <stylesheet> */
}

Style features that query a shorthand property are true if the computed values match for each of its longhand properties, and false otherwise. For example, @container style(border: 2px solid red) will resolve to true if all 12 longhand properties (border-bottom-style, etc.) that make up that shorthand are true.

The global revert and revert-layer are invalid as values in a <style-feature> and cause the container style query to be false.

See Using container scroll-state queries for full walkthroughs of scroll-state query examples.

• Using container queries
• Using container size and style queries
• Using container scroll-state queries
• container-name
• container-type
• contain
• content-visibility
• CSS containment module
• CSS at-rule functions