---
title: kIOHIDPrimaryUsageKey
framework: IOKit
role: symbol
role_heading: Macro
platforms: [Mac Catalyst 13.0+, macOS 10.0+]
path: iokit/kiohidprimaryusagekey
---

# kIOHIDPrimaryUsageKey

A key that specifies the primary usage type of the device.

## Declaration

```occ
#define kIOHIDPrimaryUsageKey
```

## Discussion

The value of this key is the number for a HID usage type.

[kIOHIDPrimaryUsageKey](kiohidprimaryusagekey.md) and [kIOHIDPrimaryUsagePageKey](kiohidprimaryusagepagekey.md) are not always rich enough to describe a device’s capabilities. Take, for example, a device that describes both a keyboard and a mouse in the same descriptor. To support this more complicated scenario, use the following keys instead:

- [kIOHIDDeviceUsageKey](kiohiddeviceusagekey.md)
- [kIOHIDDeviceUsagePageKey](kiohiddeviceusagepagekey.md)
- [kIOHIDDeviceUsagePairsKey](kiohiddeviceusagepairskey.md)

To match on only one criterion, add `kIOHIDDeviceUsageKey` and `kIOHIDDeviceUsagePageKey` to the matching dictionary. To match on multiple criteria, add `kIOHIDDeviceUsagePairsKey` to the matching dictionary.

## See Also

### Usage Keys

- [kIOHIDDeviceUsageKey](kiohiddeviceusagekey.md)
- [kIOHIDDeviceUsagePageKey](kiohiddeviceusagepagekey.md)
- [kIOHIDDeviceUsagePairsKey](kiohiddeviceusagepairskey.md)
- [kIOHIDPrimaryUsagePageKey](kiohidprimaryusagepagekey.md)