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# Characteristic Descriptors

Values that represent the UUIDs of the characteristic descriptors.

## Discussion

Use these UUIDs to add well-known descriptors to characteristics you create, or to find specific descriptors from characteristics of remote services.

## Topics

### Characteristic Descriptors

[`CBUUIDCharacteristicExtendedPropertiesString`](/documentation/CoreBluetooth/CBUUIDCharacteristicExtendedPropertiesString)

The UUID for the Extended Properties descriptor, as a string.

[`CBUUIDCharacteristicUserDescriptionString`](/documentation/CoreBluetooth/CBUUIDCharacteristicUserDescriptionString)

The UUID for the User Description descriptor, as a string.

[`CBUUIDClientCharacteristicConfigurationString`](/documentation/CoreBluetooth/CBUUIDClientCharacteristicConfigurationString)

The UUID for the Client Configuration descriptor, as a string.

[`CBUUIDServerCharacteristicConfigurationString`](/documentation/CoreBluetooth/CBUUIDServerCharacteristicConfigurationString)

The UUID for the Server Configuration descriptor, as a string.

[`CBUUIDCharacteristicFormatString`](/documentation/CoreBluetooth/CBUUIDCharacteristicFormatString)

The UUID for the Presentation Format descriptor, as a string.

[`CBUUIDCharacteristicAggregateFormatString`](/documentation/CoreBluetooth/CBUUIDCharacteristicAggregateFormatString)

The UUID for the Aggregate Format descriptor, as a string.

[`CBUUIDL2CAPPSMCharacteristicString`](/documentation/CoreBluetooth/CBUUIDL2CAPPSMCharacteristicString)

The PSM of an L2CAP channel associated with the GATT service containing this characteristic.


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