# Checkbox

> Accessible checkbox with label, indeterminate, and size variants.

- Status: stable
- Group: form
- Page: https://www.digitaltableteur.com/design-system/components/checkbox
- Contract: https://www.digitaltableteur.com/contracts/v1/Checkbox.contract.json

## When to use

Checkbox is a labelled native input for an independent yes/no choice that takes effect when the form is submitted. It supports controlled and uncontrolled use, an indeterminate state for select-all parents, and carries its own error and helper text.

## When not to use

- Do not rely on the native `indeterminate` HTML attribute; there is no such serialised attribute. Use the prop (set as a DOM property).
- Do not use a Checkbox for an immediate on/off effect; that is Switch.

## Look-alikes

- Badge: Do not use Badge as an interactive action or toggle; use Button for actions and Switch or Checkbox for state.
- Button: Do not use Button for an on/off state; use Switch. For multi-select within a group, use Checkbox or CheckboxGroup.
- Radio: Do not render a lone radio; a choice with one option is a Checkbox.
- RadioGroup: Use RadioGroup when the user picks exactly one option from an exclusive set; Checkbox is an independent yes or no choice.
- Switch: Do not use a Checkbox for an immediate on/off effect; that is Switch.

## Props

| Prop | Type | Default | Description | Required |
| --- | --- | --- | --- | --- |
| `label` | `string` | none | Label text displayed next to the checkbox. | No |
| `showLabel` | `boolean` | `true` | Whether to show the label text. | No |
| `checked` | `boolean` | none | Checked state (controlled). | No |
| `indeterminate` | `boolean` | `false` | Indeterminate (mixed) state. | No |
| `disabled` | `boolean` | `false` | Disables interaction and dims the control. | No |
| `defaultChecked` | `boolean` | none | Initial checked state for uncontrolled use. | No |
| `size` | `"sm" \| "md" \| "lg"` | `md` | Size. | No |
| `onCheckedChange` | `(checked: boolean) => void` | none | Called with the next checked value when toggled. | No |
| `id` | `string` | none | Custom ID for the checkbox element; auto-generated when omitted. | No |
| `error` | `string` | none | Error message under the control; sets aria-invalid and aria-describedby. | No |
| `helperText` | `string` | none | Supporting text under the control; always rendered, below `error` when both are set. | No |

## Variants

- Available sizes: `sm`, `md`, `lg` (default `md`).

## Invalid combinations

- MUST NOT: `checked` and `defaultChecked` set together. `checked` makes the component controlled and `defaultChecked` uncontrolled; pass one, not both.

## Keyboard

| Key | Behaviour |
| --- | --- |
| Space | Activates or toggles the focused control. (standard) |

Rows marked (standard) name a key the contract lists without a description; the behaviour shown is the usual one for that key.

## 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 NOT | `checked` and `defaultChecked` set together. `checked` makes the component controlled and `defaultChecked` uncontrolled; pass one, not both. | Checked by the MCP tool validate_component_usage. |
| MUST | ARIA: Associated label. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: Indeterminate exposes aria-checked mixed when applicable. | 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 | Every documented keyboard interaction works as specified. | Not yet verified: no evidence record. WCAG 2.1.1, 2.1.2. |
| MUST | A human completed an end-to-end accessibility review of this component. | Manual review, last on 2026-11-04. |
| SHOULD | Write the label as the positive assertion being agreed to (Subscribe to the newsletter). | Not stated in the contract. |
| SHOULD | Use indeterminate only on a select-all parent whose children are mixed; activating it resolves to checked. | Not stated in the contract. |
| SHOULD | Use the error prop for validation such as required consent; it wires aria-invalid and announces via role=alert. | Not stated in the contract. |
| SHOULD | Group related checkboxes with CheckboxGroup or FormField so a legend names the set. | Not stated in the contract. |
| SHOULD NOT | Do not hide the label with showLabel=false unless adjacent visible text names the control; the label is still the accessible name. | Not stated in the contract. |

## Install and import

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

## Links

- Machine-readable contract (Design System Contract 1.0): https://www.digitaltableteur.com/contracts/v1/Checkbox.contract.json
- Markdown version of this page: https://www.digitaltableteur.com/design-system/components/checkbox.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.