Universally Unique Identifier (UUID)

A Universally Unique Identifier (UUID) is a globally unique 128-bit (16-byte) number that is used to identify profiles, services, and data types in a Generic Attribute (GATT) profile.

For efficiency, the Bluetooth® Low Energy (BLE) specification adds support for shortened 16-bit UUIDs. These shortened formats can only be used with Bluetooth SIG defined GATT profiles.

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All UUIDs in BLE are 128-bits. In other words, a 16-bit SIG-approved UUID is actually just part of a 128-bit UUID. For example, the Client Configuration Descriptor UUID (2902) is actually 00002902-0000-1000-8000–00805f9b34fb.

Therefore, these shortened formats can only be used with UUIDs that are defined by the BLE specification.

Creating Custom UUIDs

Several tools/utilities are available for generating UUIDs. There are even web-based tools for UUID generation:

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  • A Version 1 UUID is a universally unique identifier that is generated using a timestamp and the MAC address of the computer (web server) on which it was generated.
  • A Version 4 UUID is a universally unique identifier that is generated using random numbers. The Version 4 UUIDs produced by this site were generated using a secure random number generator.

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