---
title: Null Window
framework: coregraphics
role: collectionGroup
role_heading: API Collection
path: coregraphics/null-window
---

# Null Window

Defines a guaranteed invalid window ID.

## Topics

### Constants

- [kCGNullWindowID](coregraphics/kcgnullwindowid.md)

## See Also

### Constants

- [Window Sharing Constants](coregraphics/window-sharing-constants.md)
- [Backing Store Types](coregraphics/backing-store-types.md)
- [Window List Option Constants](coregraphics/window-list-option-constants.md)
- [Window Image Types](coregraphics/window-image-types.md)
- [CGWindowID Encoding Type](coregraphics/cgwindowid-encoding-type.md)
- [Window Sharing Encoding Type](coregraphics/window-sharing-encoding-type.md)
- [Window Backing Encoding Type](coregraphics/window-backing-encoding-type.md)
- [Required Window List Keys](coregraphics/required-window-list-keys.md)
- [Optional Window List Keys](coregraphics/optional-window-list-keys.md)