Fundamentals
How we track MAC block ownership history
IEEE publishes who holds a block today, not who held it before. Our ownership timeline fills that gap. Here is where it comes from and what appears on it.
A block of MAC addresses can outlive the company that registered it. Businesses are sold, merged and renamed, and blocks can move between organizations. The IEEE registry only shows the current holder, so when a block has a recorded change, its vendor page adds a timeline of who held it and when.
Where the history comes from
| Period | Source | What the date means |
|---|---|---|
| Before our service launched | Public historical records of the IEEE registry, reaching back to the late 1990s | When the change first appeared in those records |
| Since launch | Our own monitoring of the IEEE registry, with no outside history source | When we first saw the change in the registry |
Both periods appear on one continuous timeline. In either case, a date shows when a change became public in the registry, which can be later than the sale or rename behind it. Changes from before the earliest public records are not covered.
What counts as a change
- A different organization name. This covers transfers, acquisitions, mergers and rebrands. It also covers changes to a company's legal form or the punctuation of its name.
- A move to or from private registration. IEEE lets a holder hide its identity, and we record when a block enters or leaves that status.
What does not count
- Address edits. A new office, a corrected postcode or a reformatted address, when the holder stays the same.
- Country updates. A country that differs only because the holder's address changed.
- Letter case and spacing in a name. "ACME CORP" and "Acme Corp" are the same holder.
- Registry category changes. A change to how a block is classified, with the same holder.
When an address or country changes at the same moment as the holder, the timeline notes it as part of that entry.
Why we draw the line here
The question a timeline should answer is who was responsible for a block at a given time. That matters when you investigate an old device, review historic logs or check a vendor attribution. A change of address rarely affects that answer.
Around four in five edits in the registry's recorded history leave the holder unchanged. Listing them all would bury the few entries that matter. Limiting the timeline to changes of holder keeps it short and easy to trust.
Nothing goes stale as a result. Every vendor page shows the holder's current registered address, and we update it when the registry does. We just don't keep past versions of an address as history.
When a block is no longer listed
IEEE occasionally removes a block from its registry and does not publish a reason. We keep that block instead of deleting it, because devices using it can stay in service for years. Its vendor page and lookups keep working and show the holder's last registered details, marked with the date we first saw it missing.
A block that is no longer listed appears on the timeline, but it leaves the vendor directory, our block counts and our downloads, which reflect the current registry. If IEEE lists it again, the timeline records that too.
Genuine assignments removed before our service launched are included too, from the same public records as the rest of our early history. Some of those records give no removal date, so those pages only say the block was removed before we began monitoring. Private blocks and short-lived corrupted registry entries are left out.
Reading a timeline
- No timeline on a vendor page means we have no recorded change for that block. Most blocks have never had one.
- A new name is not proof of a sale. The registry records the name, not the reason it changed, so a rebrand and an acquisition look the same.
- "Private" means the holder's identity was hidden during that period.
To see this on a real block, look up any MAC address or browse the changelog of recent registrations and ownership changes.
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