# CBUUID A universally unique identifier, as defined by Bluetooth standards. ``` class CBUUID ``` ## Overview Instances of the [`CBUUID`](/documentation/CoreBluetooth/CBUUID) class represent the 128-bit universally unique identifiers (UUIDs) of attributes used in Bluetooth low energy communication, such as a peripheral’s services, characteristics, and descriptors. This class provides a number of factory methods for dealing with long UUIDs when developing your app. For example, instead of passing around the string representation of a 128-bit Bluetooth low energy attribute in your code, you can create a [`CBUUID`](/documentation/CoreBluetooth/CBUUID) object that represents it, and pass that around instead. The Bluetooth Special Interest Group (SIG) publishes a list of commonly-used UUIDs, many of which are 16- or 32-bits for convenience. The [`CBUUID`](/documentation/CoreBluetooth/CBUUID) class provides methods that automatically transform these predefined shorter UUIDs into their 128-bit equivalent UUIDs. When you create a [`CBUUID`](/documentation/CoreBluetooth/CBUUID) object from a predefined 16- or 32-bit UUID, Core Bluetooth pre-fills the rest of the 128-bit UUID with the Bluetooth base UUID, as defined in the Bluetooth 4.0 specification, Volume 3, Part F, Section 3.2.1. In addition to providing methods for creating [`CBUUID`](/documentation/CoreBluetooth/CBUUID) objects, this class defines constants that represent the UUIDs of the Bluetooth-defined characteristic descriptors, as defined in the Bluetooth 4.0 specification, Volume 3, Part G, Section 3.3.3. ## Topics ### Creating New CBUUID Objects [`+ UUIDWithString:`](/documentation/CoreBluetooth/CBUUID/init(string:)) Creates a Core Bluetooth UUID object from a 16-, 32-, or 128-bit UUID string. [`+ UUIDWithData:`](/documentation/CoreBluetooth/CBUUID/init(data:)) Creates a Core Bluetooth UUID object from a 16-, 32-, or 128-bit UUID data container. [`+ UUIDWithCFUUID:`](/documentation/CoreBluetooth/CBUUID/init(cfuuid:)-3h0ry) Creates a Core Bluetooth UUID object from a Core Foundation UUID object. [`+ UUIDWithNSUUID:`](/documentation/CoreBluetooth/CBUUID/init(nsuuid:)-2amob) Creates a Core Bluetooth UUID object from a Foundation UUID object. ### Inspecting CBUUID Properties [`data`](/documentation/CoreBluetooth/CBUUID/data) The data of the UUID. [`UUIDString`](/documentation/CoreBluetooth/CBUUID/uuidString) The UUID represented as a string. ### UUID Constants [Characteristic Descriptors](/documentation/CoreBluetooth/characteristic-descriptors) Values that represent the UUIDs of the characteristic descriptors. ## Relationships ### Inherits From [`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class) ### Conforms To [`Equatable`](/documentation/Swift/Equatable) [`Hashable`](/documentation/Swift/Hashable) [`NSCopying`](/documentation/Foundation/NSCopying) [`CVarArg`](/documentation/Swift/CVarArg) [`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)