Use CSS container queries when a component should respond to the space available in its containing region rather than the size of the browser window. Set container-type: inline-size on an ancestor, then use @container to style its descendants at the sizes that suit your component.
How CSS container queries work
A container query tests an eligible ancestor container and conditionally applies styles to elements inside it. That lets a reusable card, panel, or other component adapt whether it appears in a narrow sidebar or a wide main column. A media query, by contrast, responds to the viewport or device characteristics, not the space occupied by an individual component.
The container must be an ancestor of the elements being styled. A query does not select an arbitrary sibling, and it is not a way to query the viewport.
Write a basic size query
Start with the component’s default appearance. Make a parent eligible for inline-size queries, then add a conditional rule for a descendant:
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<div class="post">
<article class="card">
<h2>Card title</h2>
<p>Card content</p>
</article>
</div>.post {
container-type: inline-size;
}
.card h2 {
font-size: 1em;
}
@container (width > 700px) {
.card h2 {
font-size: 2em;
}
}When the nearest eligible ancestor is wider than 700 pixels, the heading rule applies. The threshold is an illustration, not a recommended universal breakpoint; choose it based on when your component’s content and layout need to change. The default styles still apply when the condition is not met.
Choose the container type and axis
container-type determines which dimensions can be queried and what containment behavior is applied.
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| Type | What it enables | What to consider |
|---|---|---|
inline-size |
Queries the container’s inline dimension, typically its available width in a horizontal writing mode. | This is the usual choice for responsive components. It does not impose block-size containment. |
size |
Queries both inline and block dimensions. | It applies size containment: the container’s dimensions are calculated independently of its contents. Ensure its layout context or explicit sizing establishes meaningful dimensions, or it can collapse. |
Prefer the logical inline axis when the component should react to its available line direction; it is not always identical to physical width in every writing mode. Use size only when you need to query both axes and have accounted for its intrinsic-sizing effects.
Name a container when selection should be explicit
An unnamed query uses the nearest eligible ancestor. That can be surprising in nested components: an inner container may be selected instead of a farther outer region. Give the intended container a name and use that name in the condition:
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.post {
container: sidebar / inline-size;
}
@container sidebar (width > 700px) {
.card {
font-size: 2em;
}
}The container shorthand sets both the container name and type. You can instead declare container-name and container-type separately. Naming is especially helpful when components are nested or a page has several independent regions.
Use container-relative length units
Container query units let descendant lengths scale with an eligible size container, without expressing every adjustment as a breakpoint:
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cqwis one percent of the container’s physical width.cqhis one percent of its physical height.cqiis one percent of its inline size.cqbis one percent of its block size.cqminandcqmaxare the smaller and larger ofcqiandcqb.
For example, padding: 4cqi; makes padding responsive to the container’s inline size. Use these units when locally fluid spacing or type is useful; they are not necessary for every responsive layout. If no eligible container exists for the relevant axis, the unit falls back to the corresponding small viewport unit.
Choose between a media query and a container query
- Use
@mediawhen a change should follow viewport or device characteristics, such as a page-level navigation layout. - Use
@containerwhen a component’s available containing region should trigger the change, regardless of where that component is placed. - Use both when the page has viewport-level changes and individual components also need to adapt to their own regions.
Know which query features your browsers support
MDN describes the established @container feature as widely available across many devices and browser versions since February 2023. That broad availability should not be read as a guarantee that every newer query type or syntax works everywhere. MDN’s current guide distinguishes size, style, name-only, scroll-state, and anchored query types, and its reference notes that support varies for some parts. Check the compatibility information for the specific syntax and browsers you target: MDN’s @container reference.
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Style queries are a distinct feature from size queries. The MDN guide on container size and style queries describes custom-property style queries and notes that ordinary CSS declaration/property checks through style() were not supported in any browser when that guide was reviewed. The guide’s custom-property support note is dated February 2024, so check current browser compatibility rather than treating it as a current version-by-version audit.
Troubleshoot common problems
- The query appears to do nothing: Check that an ancestor has an eligible
container-type, and that the elements in the query rule are its descendants. Confirm the measured container actually crosses the threshold. - The wrong ancestor controls the result: An unnamed query selects the nearest eligible ancestor. Add a container name and reference it in
@containerto target the intended region. - The container collapses or its size changes unexpectedly: If using
container-type: size, remember that size containment calculates dimensions independently of child content. Give the element dimensions through its layout context or an explicit constraint, or useinline-sizeif only the inline dimension is needed. See MDN’scontainer-typereference. - A container-relative unit seems unexpectedly large or tracks the viewport: Check for an eligible size container on the relevant axis. Without one, the unit falls back to the corresponding small viewport unit.
- A newer query syntax fails in one browser: Verify support for that particular query type and syntax; broad support for size queries does not establish equal support for all query families.
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