# Appearance & Theming

`OnsideAppearance` sets global styling for every screen OnsideKit presents. Access the shared instance via `Onside.appearance()`.

## Set the global theme

```swift
@MainActor func setThemeMode(_ themeMode: OnsideUIThemeMode?)
```

```swift
Onside.appearance().setThemeMode(.dark)
```

`OnsideUIThemeMode`:

* `.auto` — follow the user's system appearance (Light/Dark)
* `.light` — force light
* `.dark` — force dark
* `nil` — reset the theme setting (does not affect already-presented UI)

The best place to set this is at launch:

```swift
func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
    Onside.initialize()
    Onside.appearance().setThemeMode(.dark)   // force dark for all OnsideKit screens
    return true
}
```

## Theme resolution

When OnsideKit presents a screen, the theme is resolved in this order:

1. A per-screen override from [`OnsideDelegate.onside(uiThemeOverrideForScreen:)`](/sdk/customization/delegate.md#per-screen-theme-override), if provided.
2. The global theme set here via `setThemeMode(_:)`.
3. The system appearance.

{% hint style="info" %}
Theme mode is currently the only globally configurable appearance setting.
{% endhint %}


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