https://webbluetoothcg.github.io/web-bluetooth/A device acting in either the Peripheral or Central role can host a GATT Server, which exposes a hierarchy of Services, Characteristics, and Descriptors. See § 5.1 GATT Information Model for more details about this hierarchy. Despite being designed to support BLE transport, the GATT protocol can also run over BR/EDR transport.
The first version of this specification allows web pages, running on a UA in the Central role, to connect to GATT Servers over either a BR/EDR or LE connection. While this specification cites the [BLUETOOTH42] specification, it intends to also support communication among devices that only implement Bluetooth 4.0 or 4.1.