tab-navigation

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SKILL.md

---
name: tab-navigation
description: Tabs swap views under a shared context. Use when designing tabbed layouts, settings pages, detail views or dashboards with several data views.
metadata:
  priority: 7
  pathPatterns:
    - "components/**"
    - "src/components/**"
    - "**/*.tsx"
    - "**/*.jsx"
    - "design-system/**"
    - "ui/**"
  promptSignals:
    phrases:
      - "tab"
      - "tabs"
      - "tab panel"
      - "tabbed"
      - "tab navigation"
      - "tab bar"
      - "tab strip"
      - "content switcher"
      - "pivot"
retrieval:
  aliases:
    - tab navigation
    - tab panel
    - tabbed interface
    - content switcher
    - tab bar
    - pivot control
  intents:
    - design a tabbed layout
    - add tabs to a detail view
    - organise content with tabs
    - switch between data views
    - build a settings page with tabs
  examples:
    - add tabs to this product detail page
    - design a settings screen with tab navigation
    - organise these data views with a tab strip
    - make it easy to switch between different reports
---

# Tab Navigation

Tabs organise related content under a shared context. The tab strip communicates the full set of available views; switching tabs swaps the content panel without a page navigation. They work best when all views share a heading, a primary action, or a common subject — tabs that have nothing to do with each other belong in separate pages.

---

## When to Use Tabs — and When Not To

| Use tabs when… | Use something else when… |
|---|---|
| 2–7 views share a common context (same record, same settings section) | There are more than 7–8 tabs — use a sidebar or section nav instead |
| Users switch between views frequently during a session | The content is sequential (use a stepper/wizard instead) |
| All tabs are equally valid entry points | One view is clearly primary — put the rest in a secondary nav or overflow |
| The views share a header or set of page-level actions | Each "tab" requires a different header and layout — use separate pages |

---

## Tab Types

Choose the visual style that fits the layout context.

### Underline / Indicator Tabs
A horizontal strip with a sliding underline or bottom border on the active tab. The lightest treatment — appropriate for page-level tabs where the tab strip sits inside the content area.

```
Overview  |  Activity  |  Settings
──────────
```

### Contained / Boxed Tabs
Each tab is a distinct box; the active tab appears connected to the panel below. Higher visual weight — appropriate for prominent tab groups near the top of a screen or within a card.

### Pill / Button Tabs
Rounded capsules that toggle between states. Lower emphasis — appropriate for secondary content switches within a section (not page-level). Often used for view toggles (e.g. "List / Grid / Map").

---

## Anatomy

```
┌─────────────────────────────────────────────────┐
│  Tab A  │  Tab B  │  Tab C  │                   │  ← Tab strip (role="tablist")
├─────────┴─────────────────────────────────────────┤
│                                                   │
│   Tab panel content                               │  ← Tab panel (role="tabpanel")
│                                                   │
└───────────────────────────────────────────────────┘
```

- **Tab strip:** Fixed height (typically 40–48px). Does not scroll with the page — consider making it sticky when the page is long.
- **Tab panel:** Fills the remaining available height. The panel, not the tab strip, scrolls when content overflows.
- **Active indicator:** A 2–3px bottom border in `--color-primary` for underline tabs; filled background for contained/pill tabs.

---

## States

| State | Visual treatment |
|---|---|
| Active | Primary colour indicator; label in `--color-text-primary` or primary |
| Inactive | Muted label (`--color-text-secondary`); no indicator |
| Hover | Subtle background shift (`--color-grey-50`); label slightly darkens |
| Focus | Visible focus ring (`outline: 2px solid --color-primary; outline-offset: 2px`) |
| Disabled | Reduced opacity (`0.4`); `cursor: not-allowed`; never the active tab |

Never disable the active tab. If content is unavailable, show it inside the panel with an explanation rather than disabling the tab.

---

## Tab Overflow

When the tab strip is wider than its container, do not wrap tabs onto multiple lines; it destroys the strip metaphor. Three ways out, in order of preference.

### Select fallback
Measure the strip; when its content is wider than its container, render a native `<select>` with the same options. Every option stays reachable at one glance and at any width, with nothing hidden off the edge, and the platform already gives touch users its picker.

### Scrollable strip
The strip scrolls horizontally with a fade at the right edge to signal overflow. The platform convention on mobile, and fine when the user knows the set of tabs; it hides options from a first-time reader.

```css
.tab-strip {
  display: flex;
  overflow-x: auto;
  scrollbar-width: none; /* hide scrollbar visually on desktop */
}
.tab-strip::after {
  content: '';
  position: absolute; right: 0;
  background: linear-gradient(to left, var(--color-surface), transparent);
  pointer-events: none;
}
```

### "More" overflow menu
Show as many tabs as fit, then collapse the rest into a `More ▾` dropdown. Update the "More" label when an overflowed tab is active: `Settings ▾` (showing the active hidden tab name).

Whichever is used, mark the selected tab with an underline on that tab only; a rule under the whole strip competes with it. For desktop dashboards with many views, prefer a sidebar nav over overflow tabs.

---

## Vertical Tabs

Use when there are 5+ tabs and the layout has a left sidebar. Vertical tabs allow longer labels without overflow issues and scale more gracefully.

- Fixed width sidebar (typically 200–240px) with tab labels stacked vertically
- Active tab: left border accent (`3px solid --color-primary`) + subtle background
- The main content area fills the remaining width

---

## Keyboard Navigation

Tabs follow the ARIA "roving tabindex" pattern for within-strip navigation.

| Key | Action |
|---|---|
| `Tab` | Move focus to the tab strip (then into the active panel) |
| `←` / `→` | Move between tabs (horizontal strip); activate immediately or on Enter depending on content cost |
| `↑` / `↓` | Move between tabs (vertical strip) |
| `Home` | Jump to first tab |
| `End` | Jump to last tab |
| `Enter` / `Space` | Activate focused tab (if not already auto-activating on arrow key) |

**Auto-activate vs. manual activate:** If switching tabs triggers a network request, use manual activation (arrow keys move focus, Enter activates) to avoid unnecessary fetches. If content is already loaded or cheap, auto-activation on arrow key is acceptable.

---

## ARIA

```html
<div role="tablist" aria-label="Product sections">
  <button
    role="tab"
    id="tab-overview"
    aria-selected="true"
    aria-controls="panel-overview"
    tabindex="0"
  >Overview</button>
  <button
    role="tab"
    id="tab-activity"
    aria-selected="false"
    aria-controls="panel-activity"
    tabindex="-1"
  >Activity</button>
</div>

<div
  role="tabpanel"
  id="panel-overview"
  aria-labelledby="tab-overview"
>…</div>

<div
  role="tabpanel"
  id="panel-activity"
  aria-labelledby="tab-activity"
  hidden
>…</div>
```

- `aria-selected="true"` on the active tab, `false` on all others
- `tabindex="0"` on the active tab, `-1` on all others (roving tabindex)
- `hidden` attribute (or `display: none`) on inactive panels — screen readers skip hidden panels
- `aria-label` on the `tablist` when the heading above doesn't sufficiently describe the group

---

## State Persistence

Remember the active tab across page loads and navigations:

- **URL fragment or query param:** `?tab=activity` — the most robust approach; supports deep linking and browser back/forward
- **localStorage:** Acceptable for preferences (e.g. a preferred dashboard view) that don't need to be shareable
- Do not use `sessionStorage` — tabs closing lose the state unexpectedly

When the URL contains a tab param, jump to that tab on load even if it's not the first tab.

---

## Nested Tabs

Avoid tabs within tabs. Nested tabbing creates confusion about scope — a user editing content in "Tab A › Sub-tab 2" has no clear mental model of what the outer tab means.

If you find yourself nesting tabs, reconsider the information architecture:
- Can the inner tabs become a secondary nav (pills, a sidebar within the panel)?
- Can the outer tabs become a top-level page nav instead?

One level of tabs maximum in the primary content area.

---

## Review Checklist

- [ ] Are there 2–7 tabs, each sharing a common subject or context?
- [ ] Is the tab strip not wrapping to multiple lines on any target viewport?
- [ ] Is the active tab clearly distinguished by colour and/or indicator?
- [ ] Do hover and focus states meet contrast requirements?
- [ ] Are disabled tabs avoided (showing unavailability inside the panel instead)?
- [ ] Does keyboard navigation follow roving tabindex (←/→ between tabs, Tab into panel)?
- [ ] Is `role="tablist"`, `role="tab"`, `role="tabpanel"`, and `aria-selected` set correctly?
- [ ] Are inactive panels hidden from the accessibility tree (`hidden` attribute)?
- [ ] Is the active tab persisted in the URL (for deep-linkable views) or localStorage?
- [ ] Are nested tabs avoided?
- [ ] Does tab overflow use a select, a scrollable strip or a "More" menu, never wrapping?
- [ ] Is the selected tab marked by an underline on that tab only, with no rule under the whole strip?