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About this tool
Reads the U/L and I/G bits of any MAC address to say whether it is a real vendor identity or a randomised private Wi-Fi address, and what that breaks.
This explainer classifies any MAC address by reading the two flag bits IEEE Std 802-2014 defines in the first octet: the U/L bit (0x02) says whether the address was assigned from an IEEE manufacturer block or made up locally, and the I/G bit (0x01) says whether it addresses one interface or a group. Because operating systems build private Wi-Fi addresses by setting U/L and clearing I/G, a randomised address always has 2, 6, A or E as its second hex digit — which the page shows alongside the router features a rotating address breaks. Useful to anyone puzzled by unfamiliar devices in a router list or by parental controls that quietly stopped applying.
Open MAC Randomisation Explainer on AltFTool — it loads instantly in your browser.
Add your input to the workspace.
Adjust the options until the result looks right.
Copy or download the output and put it to work.
Classification comes from the U/L and I/G bits, not from guesswork about vendor prefixes.
Colon, hyphen, Cisco dotted-quad and bare hex are all accepted and normalised.
No OUI lookup, no logging — the address you paste is analysed in the browser only.
Check the second hex digit: a private Wi-Fi address generated by an operating system is unicast and locally administered, which forces that digit to 2, 6, A or E. So 3A:2F:19:8C:41:0D is randomised, while AC:DE:48:00:11:22 comes from an IEEE-assigned manufacturer block. It is a strong signal rather than proof, because any address can be spoofed manually.
iOS 14 and later, and Android 10 and later, generate a separate randomised address per network by default so shops, airports and other venues cannot link your visits across locations into one profile. The address normally stays the same for a given network, unless you enable a rotating option or forget and rejoin the network.
Yes, whenever a rule is keyed on the address. Static DHCP reservations, MAC allow-lists, per-device schedules, bandwidth limits and presence automations all stop matching once the device presents a new address, which usually looks like the feature failing. The fix is to set that one network to use a fixed or hardware address on the device, rather than turning randomisation off everywhere.
Leave it on for public and guest networks, where it is doing real work against passive tracking, and consider a fixed private address only for your own home network if you rely on per-device rules. Turning it off globally gives every venue you visit a permanent identifier for your device.