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# UISplitViewController.SplitBehavior.overlay

The sidebars are layered on top of the secondary view controller, leaving the secondary view controller partially visible.

```
case overlay
```

## Discussion

This split behavior shows one or both sidebars layered on top of the secondary view controller, partially obscuring it. The secondary view controller is dimmed out, preventing interaction with its view.

The possible display modes for this split behavior are:

- [`UISplitViewController.DisplayMode.secondaryOnly`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/secondaryOnly)
- [`UISplitViewController.DisplayMode.oneOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/oneOverSecondary)
- [`UISplitViewController.DisplayMode.twoOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/twoOverSecondary)

If the current display mode is not [`UISplitViewController.DisplayMode.twoOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/twoOverSecondary) and [`presentsWithGesture`](/documentation/UIKit/UISplitViewController/presentsWithGesture) is <doc://com.apple.documentation/documentation/Swift/true>, the split view controller presents a special bar button item styled as a back-chevron icon. When a user taps this button, it changes the current display mode from [`UISplitViewController.DisplayMode.secondaryOnly`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/secondaryOnly) to [`UISplitViewController.DisplayMode.oneOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/oneOverSecondary), and from [`UISplitViewController.DisplayMode.oneOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/oneOverSecondary) to [`UISplitViewController.DisplayMode.twoOverSecondary`](/documentation/UIKit/UISplitViewController/DisplayMode-swift.enum/twoOverSecondary).

---

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