Every address on the internet lives in one of 65,536 blocks, and every one of those
blocks has an owner. The map below is all of IPv4 at once: 65,536 cells, one per
/16, laid out along a Hilbert curve so that numerically
adjacent blocks are visually adjacent. That single choice turns the address space
into a picture of its own history — the 1980s allocations sit together in one belt,
because that is when they were handed out.
One cell is one
/16 — 65,536 addresses. The white box is the block on trial; the
outlined tile behind it is the /8 it belongs to, and every other
outlined tile is a /8 where this dataset knows individual
/16 holders — the campus, company and laboratory blocks.
Click any cell to see who holds it.
Which organisation holds
4.120.0.0/16?
Pick one of the four owners. Same block for everyone today.
The four choices are drawn from the same kind of holder where the map has enough of them — so a car maker is up against other legacy companies, a registry against other registries.
/8 blocks, plus 12 curated
blocks
/8
/8
/8 blocks, plus 7 curated
blocks
/8
/8 blocks, plus 8 curated
blocks
/8 blocks
/8 blocks
/8 blocks
/8 blocks
This is the part of the page that is not a quiz: click anywhere on the map.
Click any cell to learn
who holds that /16.
The map is coloured by the registry that administers the /8, with the
curated holders — companies, universities, laboratories and the Pentagon — drawn
on top of it.
An address is a number, and a number is a position. Take the 65,536 /16
blocks in numerical order and walk them along a Hilbert curve — a space-filling curve
that keeps consecutive numbers next to each other at every scale — and you get the
picture above. It is why 19.0.0.0 (Ford) appears beside
17.0.0.0 (Apple), why the Pentagon’s thirteen /8s form one
contiguous region, and why the university /16s of 1985 cluster inside
128.0.0.0/8 like a campus belt.
The curve is recursive, so each /8 is exactly one aligned 16×16 tile of
its own 256 /16s, and the 256 tiles themselves follow a Hilbert curve of
order 4. A /8 is 1/256th of the whole internet — 16,777,216
addresses. A /16 is 65,536 of them: a whole campus, once. The address
space was handed out in these tiles, and the map still shows the shape of it.
Every holder, range and history line on this page comes from the IANA IPv4 Address Space Registry and from the RIR registration databases (ARIN, RIPE, APNIC, AFRINIC), snapshotted 2026-10-16 (IANA registry file last modified 2026-10-13) and shipped with the site — nothing is looked up while you wait. Where a block’s IANA designation names an organisation outright, the reveal says so; where the registry lists a large block as “legacy space”, the reveal names both the registry that administers it and the organisation that once held it.
Dataset: IANA IPv4 Address Space Registry (ipv4-address-space.csv) for the 256 /8 designations; IANA RDAP bootstrap + ARIN/RIPE/APNIC/AFRINIC RDAP queries for every registered range below; Wikipedia “List of assigned /8 IPv4 address blocks” for the history lines. Frozen 2026-10-16 (IANA registry file last modified 2026-10-13).
The tools behind this mechanic: Country hub ASN hub IPv4 blocks by country
Prefer countries? There is the daily IP puzzle. Prefer networks? There is the daily network puzzle. Prefer reasoning from a measurement? Ping Detective gives you five round-trip times and a world map. The route globe draws a real traceroute, and the tools will look an address up for you.
This page is in daily mode for 2026-10-23. The daily round is the same for everyone on a given UTC day; a practice round is the same for everyone who asks for the same number.