BSSID
Basic Service Set Identifier
The MAC address of a Wi-Fi access point's radio interface — the unique hardware identifier that distinguishes one AP from another, even when they share the same network name.
A BSSID is the Layer 2 MAC address of a specific Wi-Fi radio interface on an access point. When your router broadcasts a 2.4 GHz and a 5 GHz network with the same SSID name, each radio has its own BSSID — they are physically different radios, each with a distinct hardware address. In a mesh or enterprise system with dozens of APs on the same SSID, each AP radio has a unique BSSID. This is how your device tracks which physical radio it is currently associated with.
BSSID vs SSID vs ESSID
| Term | What it is | Scope | Example |
|---|---|---|---|
| SSID | Human-readable network name | One AP or shared across many | HomeNetwork |
| BSSID | MAC address of one AP radio | Single radio interface | aa:bb:cc:dd:ee:ff |
| ESSID | Extended SSID — same name across multiple APs | Entire roaming domain | HomeNetwork on AP1, AP2, AP3 |
Multiple BSSIDs on one physical AP
A single physical access point typically exposes several BSSIDs simultaneously. A dual-band router has at least two: one for the 2.4 GHz radio and one for the 5 GHz radio. If the router also broadcasts a guest network on each band, that adds two more — four BSSIDs from a single device. Tri-band routers (2.4 + 5 + 6 GHz) have at least three. Enterprise APs commonly broadcast eight or more virtual BSSIDs per radio, each mapped to a different VLAN and SSID for different user groups. Each BSSID sends its own beacon frames at the configured interval (typically every 100 ms).
How devices use BSSID for roaming
When multiple APs share the same SSID (an ESSID), your device scans for beacon frames from all nearby BSSIDs advertising that SSID and selects the one with the strongest signal. As you move, the device may roam from one BSSID to another — ideally transparently, using 802.11r fast BSS transition to re-authenticate in under 50 ms. The BSSID is the identifier your device tracks at the 802.11 layer; the SSID is just the name used for initial discovery and display.
How to see your current BSSID
- Linux:
iw dev wlan0 link— shows connected BSSID, frequency, and signal strength - macOS: hold Option and click the Wi-Fi menu bar icon — BSSID is listed alongside channel, RSSI, and noise; or use
airport -Iin Terminal (path:/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport) - Windows:
netsh wlan show interfaces— listed as "BSSID" in the output - Android/iOS: shown in the connected network details screen in Settings (varies by OS version)
BSSID in beacon frames
Every Wi-Fi access point continuously transmits beacon frames — management frames broadcast at regular intervals (default 100 ms, or 10 per second) that announce the network's existence. Each beacon contains the BSSID as the source MAC address, the SSID, supported data rates, channel information, and capability flags (supported security modes, QoS parameters, etc.). Passive scanning devices listen for beacons to discover available networks without transmitting themselves.
Randomised BSSIDs and privacy
Traditionally, BSSIDs were fixed hardware MAC addresses — stable identifiers that could be used to fingerprint and track physical AP locations. Recent Wi-Fi standards and OS implementations have introduced MAC address randomisation on the client side (randomising the client's own MAC when scanning), but AP BSSIDs themselves remain stable hardware addresses in virtually all current deployments. Some newer enterprise systems generate locally-administered BSSIDs for virtual SSIDs, but these are not randomised in the privacy sense — they are fixed per-configuration.
Frequently Asked Questions
What is the difference between SSID and BSSID?
SSID is the human-readable network name you see in your Wi-Fi list. BSSID is the MAC address of the specific access point radio broadcasting that name. Multiple APs can share the same SSID but each radio has a unique BSSID.
Why does locking to a BSSID improve Wi-Fi performance?
When multiple APs share the same SSID, your device may roam to a weaker AP. Locking to a specific BSSID forces it to stay on the chosen radio — useful when unexpected roaming causes slow speeds or disconnections during troubleshooting.
How is BSSID used for location services?
Location services maintain databases of BSSID-to-coordinate mappings built from GPS-correlated wardriving data. A device scanning for nearby Wi-Fi can estimate its position by matching visible BSSIDs against this database — without GPS and without connecting to any network.