What Is Container Query Builder?
Container Query Builder generates CSS container queries — the modern alternative to media queries that lets components respond to their parent container’s size rather than the viewport. This makes truly reusable, context-aware components that adapt whether they’re in a sidebar, a main column, or a full-width section.
How to Use This Tool
Define your container element and set breakpoint conditions (min-width, max-width, aspect-ratio). Add the CSS rules you want applied at each breakpoint, and preview the responsive behavior in real time by resizing the container. Copy the generated CSS when you’re satisfied. Everything runs in your browser.
Why Use Container Query Builder?
Container queries are powerful but their syntax is new and easy to get wrong. This tool provides a visual builder that lets you see the responsive behavior immediately, eliminating guesswork. It generates clean, production-ready CSS you can drop into any project — for free and with no signup. For a detailed walkthrough, see our step-by-step guide.
Common Use Cases
Card components that appear in both a narrow sidebar and a wide hero region, where media queries fail because the viewport is the same in both placements but the container is not. Reusable layout primitives in a design system, sized to whatever slot they end up in. Email-style two-column layouts that need to collapse when the parent shrinks below a threshold, regardless of viewport width.
Dashboard widgets that get rearranged by users into different grid cells — each widget knows its own container size and adapts independently. Marketing site blocks that ship in different page templates with different surrounding constraints. Migrating a mature design system from media-query-based responsive logic to container-based, where the builder helps shape the syntax of the new @container rules.
How We Compare
Plain @media queries match against the viewport, which makes them the wrong primitive for component-level responsive behavior. JavaScript-based size observers (the ResizeObserver API plus a class toggle) can simulate container behavior but run on the main thread and introduce a hydration flicker on the first paint.
Container queries are the right primitive for this problem and now have stable support in all modern engines. This builder helps you compose the container-type declaration on the parent and the matching @container rules on the children, which is the part that's easy to get wrong by hand. For the broader breakpoint layer of a project, see responsive breakpoint previewer.
One practical note: container queries require declaring container-type: inline-size (or size) on the parent before @container rules can match. The builder includes that declaration in its output, but it's the most common reason hand-written container queries silently fail — worth checking first when something isn't responding.
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools