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# CGOpenGLDisplayMask

A bitmask used in OpenGL to specify a set of attached displays.

```
typealias CGOpenGLDisplayMask = UInt32
```

## Discussion

In macOS, OpenGL can provide information about the capabilities of the hardware renderers driving a specified set of displays. A 32-bit mask is used to specify the displays—each bit in the mask represents a single display.

To learn how to find the mask bit that corresponds to a given display, see the function [`CGDisplayIDToOpenGLDisplayMask(_:)`](/documentation/CoreGraphics/CGDisplayIDToOpenGLDisplayMask(_:)).

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