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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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.
Browse by registry
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Countries with the most unannounced blocks, largest first.
Unannounced blocks in United States
26,993 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 151.171.0.0/16 | 65.5k | ARIN |  US | 5th Sept 1991 |
| 151.174.0.0/16 | 65.5k | ARIN | US | 5th Sept 1991 |
| 151.181.128.0/19 | 8.2k | ARIN | US | 17th Sept 1991 |
| 151.181.176.0/20 | 4.1k | ARIN | US | 17th Sept 1991 |
| 151.185.0.0/19 | 8.2k | RIPE NCC | US | 17th Sept 1991 |
| 151.185.128.0/18 | 16.4k | ARIN | US | 8th Jul 2026 |
| 151.209.0.0/16 | 65.5k | ARIN | US | 25th Sept 1991 |
| 151.210.64.0/19 | 8.2k | ARIN | US | 31st Jul 2026 |
| 152.100.0.0/16 | 65.5k | ARIN | US | 12th Sept 1991 |
| 152.116.0.0/16 | 65.5k | ARIN | US | 13th Aug 1991 |
| 152.117.32.0/20 | 4.1k | ARIN | US | 13th Aug 1991 |
| 152.140.0.0/15 | 131k | ARIN | US | 22nd Aug 1991 |
| 152.142.0.0/16 | 65.5k | ARIN | US | 22nd Aug 1991 |
| 152.144.0.0/16 | 65.5k | ARIN | US | 22nd Aug 1991 |
| 152.146.0.0/16 | 65.5k | ARIN | US | 23rd Aug 1991 |
| 152.159.0.0/16 | 65.5k | ARIN | US | 18th Mar 1992 |
| 152.161.0.0/16 | 65.5k | ARIN | US | 1st Apr 1992 |
| 152.162.0.0/16 | 65.5k | ARIN | US | 1st Apr 1992 |
| 152.224.0.0/15 | 131k | ARIN | US | 23rd Sept 1991 |
| 152.228.96.0/19 | 8.2k | ARIN | US | 30th Sept 1991 |
| 152.234.192.0/18 | 16.4k | RIPE NCC | US | 6th Mar 2025 |
| 152.235.0.0/17 | 32.8k | ARIN | US | 9th Feb 2026 |
| 152.238.0.0/16 | 65.5k | ARIN | US | 29th Jul 2026 |
| 152.239.128.0/17 | 32.8k | ARIN | US | 29th Jul 2026 |
| 152.36.16.0/20 | 4.1k | ARIN | US | 21st Jul 2026 |
| 152.36.32.0/19 | 8.2k | ARIN | US | 10th Jan 1992 |
| 152.36.64.0/18 | 16.4k | ARIN | US | 10th Jan 1992 |
| 152.36.8.0/21 | 2k | ARIN | US | 11th Aug 2026 |
| 152.55.0.0/18 | 16.4k | ARIN | US | 28th Jul 2026 |
| 152.55.192.0/20 | 4.1k | ARIN | US | 23rd Jan 2026 |
| 152.55.248.0/22 | 1k | ARIN | US | 26th Feb 2026 |
| 152.55.252.0/22 | 1k | ARIN | US | 28th Apr 2026 |
| 152.64.0.0/16 | 65.5k | ARIN | US | 19th Aug 1991 |
| 152.68.0.0/16 | 65.5k | ARIN | US | 21st Aug 1991 |
| 153.14.0.0/16 | 65.5k | ARIN | US | 16th Sept 1991 |
| 153.15.0.0/16 | 65.5k | RIPE NCC | US | 1st Sept 1993 |
| 153.16.0.0/16 | 65.5k | ARIN | US | 17th Sept 1991 |
| 153.30.0.0/16 | 65.5k | ARIN | US | 23rd Sept 1991 |
| 153.4.0.0/16 | 65.5k | ARIN | US | 12th Sept 1991 |
| 153.40.0.0/16 | 65.5k | ARIN | US | 3rd Jan 1992 |
| 153.50.0.0/16 | 65.5k | ARIN | US | 10th Jun 1992 |
| 153.52.128.0/19 | 8.2k | ARIN | US | 23rd Sept 1991 |
| 153.52.224.0/19 | 8.2k | ARIN | US | 5th Jun 2026 |
| 153.55.0.0/17 | 32.8k | ARIN | US | 23rd Sept 1991 |
| 153.55.192.0/18 | 16.4k | ARIN | US | 23rd Sept 1991 |
| 153.57.224.0/19 | 8.2k | ARIN | US | 10th Apr 2026 |
| 153.58.0.0/16 | 65.5k | ARIN | US | 23rd Sept 1991 |
| 153.60.64.0/18 | 16.4k | ARIN | US | 6th Apr 2026 |
| 153.62.0.0/16 | 65.5k | ARIN | US | 23rd Sept 1991 |
| 153.63.0.0/16 | 65.5k | ARIN | US | 23rd Sept 1991 |