# AspectRatio

> Layout primitive that locks its children to a fixed width/height ratio (1:1, 4:3, 16:9, …) so media-shaped containers reserve space before content loads.

- Status: beta
- Group: structure
- Page: https://www.digitaltableteur.com/design-system/components/aspect-ratio
- Contract: https://www.digitaltableteur.com/contracts/v1/AspectRatio.contract.json

## When to use

AspectRatio reserves a proportional box and absolutely fills it with its child, clipping overflow. Wrap media; images, video embeds, map iframes; and let the child fill (width/height 100%, object-fit cover). Because the box takes its height from the ratio, it also works as a CLS-free placeholder while media loads. 16:9 is the default; 1:1 suits avatars and thumbnails.

## When not to use

- Do not use this as a generic flex/grid item; pick a layout primitive instead.
- Do not add padding or margin via className; children will overlap their own padding because the wrapper is `position: relative`.

## Look-alikes

The contract names no look-alike with a deciding condition.

## Props

| Prop | Type | Default | Description | Required |
| --- | --- | --- | --- | --- |
| `children` | `ReactNode` | none | Media or placeholder content inside the ratio box. | Yes |
| `ratio` | `"1:1" \| "4:3" \| "16:9" \| "21:9" \| "3:2" \| "2:3"` | `16:9` | Width-to-height ratio token. | No |
| `className` | `string` | none | Additional CSS class names. | No |

## Variants

- Allowed `ratio` values: `1:1`, `4:3`, `16:9`, `21:9`, `3:2`, `2:3` (default `16:9`).

## Invalid combinations

The contract records no invalid combinations.

## Keyboard

The contract records no keyboard interaction.

## Rules

Every item under When not to use is a MUST NOT. MUST and SHOULD follow RFC 2119.

| Level | Rule | How it is checked |
| --- | --- | --- |
| MUST | ARIA: No own ARIA; the wrapper inherits semantics from its children. Author the inside as a meaningful region (img, figure, iframe) yourself. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | Required stories produce no axe violations at the configured severity. | Automated by `npm run test:stories:matrix:ci`. WCAG 2.5.8. |
| MUST | The accessibility tree (role, name, state) matches the committed snapshot for every required story. | Automated by `npm run test:stories:matrix:ci`. WCAG 1.3.1, 4.1.2. |
| MUST | The component remains legible and operable under a real browser forced-colors: active pass. | Automated by `npm run test:stories:hc`. |
| MUST | A human completed an end-to-end accessibility review of this component. | Manual review, last on 2026-05-28. |
| SHOULD | Make the child fill: width/height 100% and object-fit cover for images. | Not stated in the contract. |
| SHOULD | Use 16:9 for video, 1:1 for square thumbnails, 3:2 for editorial photography. | Not stated in the contract. |
| SHOULD | Wrap lazy media in it so the page reserves space up front (no layout shift on load). | Not stated in the contract. |
| SHOULD | Combine with Skeleton inside for a loading placeholder at the final footprint. | Not stated in the contract. |
| SHOULD NOT | Do not put text layouts inside; overflow hidden clips anything the ratio cannot fit. | Not stated in the contract. |
| SHOULD NOT | Do not nest ratio boxes; one box defines the frame, the child just fills it. | Not stated in the contract. |

## Install and import

- Install: `npm install @digitaltableteur/react` (version 0.9.1, restricted access on npm).
- Import: `import { AspectRatio } from "@digitaltableteur/react";`
- Entry point: `@digitaltableteur/react/layout` exports it too.
- Styles: import `@digitaltableteur/react/style.css` once at the app boundary.
- Also available as the custom element `<dt-aspect-ratio>`; see the custom elements manifest.

## Links

- Machine-readable contract (Design System Contract 1.0): https://www.digitaltableteur.com/contracts/v1/AspectRatio.contract.json
- Markdown version of this page: https://www.digitaltableteur.com/design-system/components/aspect-ratio.md
- Component index as JSON: https://www.digitaltableteur.com/design-system/components.json
- All components: https://www.digitaltableteur.com/design-system/components
- Source: The implementation lives in a private repository. This page, its Markdown twin and the contract are generated from it at build time and are the public source of truth.