# BlogCategoryFilter

> Single-select tag filter for the blog archive: a labelled group of toggle chips with an implicit All, three visual treatments, optional per-tag counts and an optional collapsed mode.

- Status: stable
- Group: navigation
- Page: https://www.digitaltableteur.com/design-system/components/blog-category-filter
- Contract: https://www.digitaltableteur.com/contracts/v1/BlogCategoryFilter.contract.json

## When to use

Category filter control for the blog archive. Blog-scoped variant; for generic list pages use CategoryFilter.

## When not to use

- Do not use this for generic list pages; that is CategoryFilter.

## Look-alikes

- CategoryFilter: Do not use this for generic list pages; that is CategoryFilter.

## Props

| Prop | Type | Default | Description | Required |
| --- | --- | --- | --- | --- |
| `tags` | `string[]` | none | Array of unique tags. | Yes |
| `selectedTag` | `string \| null` | none | Currently selected tag (null means "All") | Yes |
| `onTagChange` | `(tag: string \| null) => void` | none | Callback when tag selection changes. | Yes |
| `showCounts` | `boolean` | `false` | Show post counts per tag. | No |
| `tagCounts` | `Record<string, number>` | `{}` | Tag counts object. | No |
| `variant` | `"pills" \| "underline" \| "minimal"` | `pills` | Style variant. | No |
| `size` | `"sm" \| "md" \| "lg"` | `md` | Size variant. | No |
| `collapsible` | `boolean` | `false` | Collapse to the selected chip and a disclosure button; expanding shows every chip and picking one collapses back to it. | No |
| `className` | `string` | none | Custom className. | No |

## Variants

- Available variants: `pills`, `underline`, `minimal` (default `pills`).
- Available sizes: `sm`, `md`, `lg` (default `md`).

## Invalid combinations

The contract records no invalid combinations.

## Keyboard

| Key | Behaviour |
| --- | --- |
| Tab | Moves to and through the filter buttons. |
| Enter/Space | Or click activates the focused filter. |
| General | With collapsible, a disclosure button is the first child of the group; Enter/Space or click shows or hides the chips. |

## 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: Role=group labelled via blogFilterByTag; each filter is a toggle button with aria-pressed. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: Single-select: exactly one filter has aria-pressed=true at a time (visual + aria-pressed convey the active filter) | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: With collapsible, the disclosure button carries aria-expanded (no aria-controls: it sits inside the group) and an aria-label from blogFilterAllTopics; its caret icon is aria-hidden. | 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. |
| MUST NOT | Maintainers: Do not invent parallel primitives inside this folder. | Release review; not machine-checked. |

## Install and import

- In-repo only. BlogCategoryFilter is not exported from `@digitaltableteur/react`, so there is no public import path.

## Links

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