Data sources and methodology.

Who operates this

macadress.com is a product of ApisOS FZE. See the about page for the longer version.

Primary data source

All vendor and block data comes from IEEE's own public registries: MA-L (the classic 24-bit OUI), MA-M (28-bit), MA-S (36-bit, also called OUI-36), IAB (36-bit, IEEE's now-retired predecessor to MA-S, existing assignments still valid), and CID (Company ID, not a hardware OUI). We don't maintain a second-hand or purchased database; every registered block traces back to one of these five IEEE registries.

Synchronization frequency

A background service pulls all five registries on a recurring schedule (once daily, by default) and only writes rows that actually changed: each fetch is a conditional request against the source, so an unchanged registry costs nothing but a cache check. The downloadable database files on the downloads page are rebuilt from that data on their own schedule (twice daily, by default), independent of the ingestion run. Both schedules are configurable per deployment; the values above are this site's defaults, not a contractual SLA.

Last successful synchronization: Aug 22, 2026, 03:00 UTC.

How matching works

A MAC address is matched against the narrowest registered block first: a 36-bit MA-S/IAB/CID prefix takes priority over a 28-bit MA-M prefix, which takes priority over a 24-bit MA-L prefix, since smaller blocks are carved out of a larger organization's OUI and share its first three octets. A lookup that only checked the first 24 bits would misattribute every MA-M and MA-S assignment to whichever MA-L organization happens to hold the shared prefix; this site always matches the complete registered block, at whatever size IEEE actually assigned it.

When a registry re-publishes a record IEEE has already assigned (a corrected organization name, for instance), the new sync run overwrites the existing row for that exact prefix and block size. The most recent successful sync is always what's live; there's no manual conflict resolution step, because there's nothing to reconcile beyond taking IEEE's latest published version.

How randomization confidence is estimated

Randomization can't be detected directly. What can be read from the address itself is whether the U/L (universal/local) bit is set, which is necessary but not sufficient: privacy randomization, a virtual machine or container's generated address, and a manually configured address can all set the same bit. This site's confidence estimate weighs a few more signals from the address before labeling it: whether it falls in a SLAP quadrant IEEE reserves for other purposes rather than device interfaces (which rules randomization out), and whether the non-OUI bytes are all zero, a pattern far more consistent with a deliberately constructed placeholder than genuine randomness (which caps the result at "possible" rather than "likely"). Every result exposes this as one of three levels (none, possible, likely) with the reasoning in plain English, never a bare true/false.

Known limitations

• Address capacity is the size of a registered block. It is not, and can't be, a count of devices actually manufactured, sold, or currently online.
• The derived EUI-64 and IPv6 link-local fields are a mathematical derivation from the MAC address supplied. They don't confirm that any device is currently reachable at that address.
• Registration identifies the organization holding a block, never a specific device model, unit, owner, or physical location.
• A locally administered address can come from privacy randomization, a virtual machine, a container, or manual configuration; this site estimates a likelihood, not a certainty.
• IEEE's published organization names and addresses are reproduced as published, including any gaps, inconsistencies, or delays on IEEE's own side.

Correction and removal requests

If a registered organization's details look wrong here, the fastest fix is usually a correction filed directly with IEEE, since this site mirrors their registry rather than maintaining its own. If something on this site itself looks broken, stale beyond what the schedule above would explain, or you believe a listing shouldn't be published, get in touch and we'll look into it.

Privacy of submitted addresses

MAC addresses looked up through the web tool or API aren't tied to your identity or account. See the privacy policy for the full detail on request logging and retention.

Trademarks and affiliation

macadress is an independent service and is not affiliated with or endorsed by IEEE, Cisco, Wireshark, Nmap, or any hardware vendor named in its results or downloads. See the terms page for the full statement.

Changelog

No public changelog is published at this time.