# Switch
URL: https://remocn.dev/docs/ui/components/switch

A switch whose checked/unchecked state is a pure function of the timeline

- Install: `npx shadcn@latest add @remocn/switch`
- Vibe: clean
- Natural length: 120f @ 30fps

A state atom whose appearance (checked, unchecked) is a pure function of the `state` prop. Pass a state directly or drive it from the Remotion timeline via `useCurrentState`. The component reads no frame — only the state value you give it.

## Installation

```bash
npx shadcn@latest add @remocn/switch
```

> **Note**
>
> Installing `switch` automatically installs the shared `remocn-ui` core (`lib/remocn-ui/`) via `registryDependencies`. You do not need to install it separately.

## States

`SwitchState` is:

```ts
type SwitchState =
  | "unchecked"  // track = theme.input, thumb at left
  | "checked"    // track fills primary, thumb slides to the right
```

`checked` fills the track with `primary` and slides the thumb to the right edge. `unchecked` renders an inactive track with the theme input color and positions the thumb at the left.

## Snap usage

Pass `state` directly — the component snaps instantly to that visual. Useful for static previews or when you drive state from your own logic:

```tsx
import { Switch } from "@/components/remocn/switch";

export const Scene = () => <Switch state="checked" />;
```

To drive state from the timeline, use `useCurrentState`:

```tsx
import { useCurrentState } from "@/lib/remocn-ui";
import { Switch } from "@/components/remocn/switch";

export const Scene = () => {
  const state = useCurrentState(
    [
      { at: 18, state: "checked" },
      { at: 78, state: "unchecked" },
    ],
    "unchecked",
  );

  return <Switch label="Enable notifications" state={state} />;
};
```

Each `at` is a **Sequence-local authored frame**. State persists between steps: `checked` at frame 18 keeps the switch on until `unchecked` fires at frame 78. See [Concepts](/docs/ui/concepts) for the full `useCurrentState` API.

## Smooth transitions

State changes via `state` snap with no cross-fade. For animated transitions, use `useSwitchTransition` from the copied `use-switch-transition.ts` file. It reads the frame, interpolates between state presets, and returns a resolved `SwitchStyle` — pass it to the `style` prop:

```tsx
import { Switch } from "@/components/remocn/switch";
import { useSwitchTransition } from "@/components/remocn/use-switch-transition";

export const Scene = () => {
  const style = useSwitchTransition([
    { at: 18, state: "checked", duration: 14 },
    { at: 78, state: "unchecked", duration: 12 },
  ]);
  return <Switch label="Enable notifications" style={style} />;
};
```

The `duration` field on each step overrides the file's `DEFAULT_DURATION` for that specific transition. To globally tune timing and easing, edit `use-switch-transition.ts` directly in your project — that file is yours (shadcn "own your code" philosophy).

`style` takes precedence over `state` when both are provided.

## Props

| Prop | Type | Default | Description |
|---|---|---|---|
| `state` | `"unchecked" \| "checked"` | `"unchecked"` | Current visual state (snap path). State changes snap — no automatic cross-fade. |
| `style` | `SwitchStyle` | — | Resolved animated visual (smooth path). Pass an interpolated SwitchStyle from useSwitchTransition. Takes precedence over state when provided. |
| `label` | `string` | — | Optional text label rendered next to the track. Omit for a bare switch. |
| `size` | `"sm" \| "default" \| "lg"` | `"default"` | Track and label size preset. |
| `theme` | `Partial<RemocnTheme>` | — | Per-component theme override. Merges with the active RemocnUIProvider theme and the mode defaults. Must be concrete oklch/hex/rgb values — not CSS custom properties. |
| `primary` | `string` | — | Convenience override for the primary theme token — merged into theme. |
| `mode` | `"light" \| "dark"` | `"light"` | Sets the base palette. Overrides the mode on RemocnUIProvider when both are present. |
| `className` | `string` | — | Optional className passed to the switch element. |

## Use when
- Showing a toggle being flipped in a settings panel walkthrough.
- Demonstrating a binary on/off control with an animated thumb slide and track fill.
- Composing a settings scene alongside `select` and `slider` (used in `settings-toggle-flow`).

## Don't use when
- The choice is one of multiple mutually exclusive options — use `radio` or `select` instead.
- You need a compact segmented control — use `toggle-group` instead (continuous sliding indicator between segments).
- The state is a range value — use `slider` instead.