BSSID (Basic Service Set Identifier) is the unique identifier for a Wi-Fi cell. In normal networks it is the MAC address of the access point’s radio interface. An access point can host several Wi-Fi networks at once, and each one is a separate BSS with its own BSSID. Across a building the same SSID appears on many access points, so you will see many different BSSIDs for that one network, often one per access point and per band. Devices use the BSSID to choose where to connect and to decide when to roam. When you move from one access point to another the SSID can stay the same but the BSSID changes. The BSSID is advertised in beacons and probe responses and shows up in wireless scans, which makes it useful for surveys and troubleshooting. In ad hoc networks the BSSID is a locally generated address rather than a hardware MAC. Attackers can spoof a BSSID to build an evil twin or to send targeted deauthentication frames, so duplicates in odd places are a warning sign. BSSID is not the same as the SSID (the human-readable name) and not the same as the Wi-Fi 6 “BSS colour”, which is a small number used to help devices tell overlapping cells apart.
