https://www.bluetooth.com/specifications/
https://www.bluetooth.com/specifications/working-groups
https://www.bluetooth.com/specifications/specs/
Core Specification:
https://www.bluetooth.com/specifications/specs/core-specification-5-4/
https://www.bluetooth.com/specifications/specs/core-specification-5-0/
https://www.bluetooth.com/specifications/specs/core-specification-4-2/
https://www.bluetooth.com/specifications/specs/core-specification-3-0-hs/
The building blocks of all Bluetooth devices
Bluetooth® specifications define the technology building blocks that developers use to create the interoperable devices that make up the thriving Bluetooth ecosystem. Bluetooth specifications are overseen by the Bluetooth Special Interest Group (SIG) and are regularly updated and enhanced by Bluetooth SIG Working Groups to meet evolving technology and market needs.