Allocated but unannounced space
Every block here was allocated or assigned by a regional internet registry, and none of them appeared in any routing table we collected at our last snapshot — neither as a route of their own, nor covered by a larger announcement, nor carved up into more specifics.
“Unannounced” does not mean “unused”
Plenty of allocated space is deliberately kept off the public internet: private interconnects, lab and lawful-intercept ranges, networks reachable only inside one operator, and space held in reserve. Some of it is announced somewhere our collectors cannot see, which is a limit of our vantage points rather than a fact about the block.
It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today. Nothing on this page means a block is unallocated, available, or free to announce.
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Countries with unannounced space registered through ARIN, largest first.
Unannounced blocks in United States
26,273 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 131.143.55.0/24 | 256 | ARIN |  US | 7th Oct 2025 |
| 131.143.56.0/24 | 256 | ARIN | US | 7th Oct 2025 |
| 131.143.57.0/24 | 256 | ARIN | US | 22nd Oct 2025 |
| 131.143.60.0/23 | 512 | ARIN | US | 7th Oct 2025 |
| 131.143.78.0/24 | 256 | ARIN | US | 7th Oct 2025 |
| 131.143.79.0/24 | 256 | ARIN | US | 7th Oct 2025 |
| 131.143.81.0/24 | 256 | ARIN | US | 10th Oct 2025 |
| 131.143.83.0/24 | 256 | ARIN | US | 10th Oct 2025 |
| 131.143.88.0/24 | 256 | ARIN | US | 8th Oct 2025 |
| 131.143.92.0/23 | 512 | ARIN | US | 7th Oct 2025 |
| 131.143.95.0/24 | 256 | ARIN | US | 7th Oct 2025 |
| 131.149.0.0/19 | 8.2k | ARIN | US | 27th Nov 2017 |
| 131.149.128.0/18 | 16.4k | ARIN | US | 27th Nov 2017 |
| 131.149.192.0/19 | 8.2k | ARIN | US | 27th Nov 2017 |
| 131.149.252.0/22 | 1k | ARIN | US | 27th Nov 2017 |
| 131.149.32.0/20 | 4.1k | ARIN | US | 27th Nov 2017 |
| 131.149.48.0/22 | 1k | ARIN | US | 27th Nov 2017 |
| 131.149.56.0/21 | 2k | ARIN | US | 27th Nov 2017 |
| 131.149.64.0/18 | 16.4k | ARIN | US | 27th Nov 2017 |
| 131.150.11.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.12.0/22 | 1k | ARIN | US | 23rd Nov 1988 |
| 131.150.130.0/23 | 512 | ARIN | US | 23rd Nov 1988 |
| 131.150.190.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.31.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.4.0/23 | 512 | ARIN | US | 27th Nov 2017 |
| 131.150.48.0/22 | 1k | ARIN | US | 27th Nov 2017 |
| 131.150.52.0/23 | 512 | ARIN | US | 27th Nov 2017 |
| 131.150.54.0/24 | 256 | ARIN | US | 27th Nov 2017 |
| 131.150.55.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.56.0/22 | 1k | ARIN | US | 27th Nov 2017 |
| 131.150.6.0/24 | 256 | ARIN | US | 27th Nov 2017 |
| 131.150.60.0/23 | 512 | ARIN | US | 27th Nov 2017 |
| 131.150.62.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.63.0/24 | 256 | ARIN | US | 27th Nov 2017 |
| 131.150.7.0/24 | 256 | ARIN | US | 23rd Nov 1988 |
| 131.150.8.0/23 | 512 | ARIN | US | 27th Nov 2017 |
| 131.150.80.0/22 | 1k | ARIN | US | 23rd Nov 1988 |
| 131.153.248.0/24 | 256 | ARIN | US | 16th Jan 2018 |
| 131.153.249.0/24 | 256 | ARIN | US | 13th Jan 2026 |
| 131.153.252.0/22 | 1k | ARIN | US | 20th Dec 2017 |
| 131.157.0.0/16 | 65.5k | ARIN | US | 6th Dec 1988 |
| 131.192.0.0/16 | 65.5k | ARIN | US | 4th Jan 1989 |
| 131.208.0.0/16 | 65.5k | ARIN | US | 16th Jan 1989 |
| 131.209.0.0/16 | 65.5k | ARIN | US | 16th Jan 1989 |
| 131.223.0.0/16 | 65.5k | ARIN | US | 27th Jul 2018 |
| 131.253.0.0/24 | 256 | ARIN | US | 13th Feb 1989 |
| 131.253.10.0/23 | 512 | ARIN | US | 13th Feb 1989 |
| 131.253.16.0/23 | 512 | ARIN | US | 22nd Jun 2011 |
| 131.253.18.0/24 | 256 | ARIN | US | 22nd Jun 2011 |
| 131.253.19.0/24 | 256 | ARIN | US | 13th Feb 1989 |