Summary

  • ARIN reported 372,877 /24 equivalents of legacy space outside agreements in Q3 2026, 81% below Q1 2024.
  • The remainder is concentrated: 715 /16 blocks hold 49.1%, while small blocks dominate the record count.

ARIN’s Q3 2026 presentation gives the programme two scoreboards. By volume, 372,877 /24 equivalents remained outside an agreement, 26,313 fewer than the previous quarter and 81% below Q1 2024. By block count, 16,212 legacy CIDR blocks remained, down 331 in the quarter and 6,578 since Q1 2024.

Prefix size pulls the two measures apart. Blocks from /21 through /24 make up 91.5% of the count but carry just 5.9% of the remaining space. Add /17 through /20 and the smaller blocks reach 95.5% of entries but only 12.5% of volume. At the other end, 715 /16s account for 49.1% of the space. Twenty-three blocks of /15 or larger hold another 38%; there were 164 in Q1 2024.

The list is crowded with small entries; the address volume sits in a handful of large prefixes. ARIN’s /16 outreach table separately counts organizations: 28 with no contact information in the organization record and 586 in the verification pipeline, including 274 mixed organizations and 312 standalone holders. Those numbers count organizations. The 715 figure counts /16 blocks. Combine the units and the dashboard starts doing arithmetic with a straight face.

In Q4 2025, 2,768 prefixes totalling 1.28 million /24 equivalents came under Registration Services Agreements. ARIN called it the programme’s largest quarterly change, driven mainly by large legacy allocations. That leap is a poor metronome for an ordinary quarter.

Agreement status affects service access. ARIN says legacy holders outside an agreement can maintain unique Whois/RDAP registration, update public data, manage reverse DNS and registry records, and use DNSSEC. RPKI and IRR access require an ARIN agreement. Agreement coverage, contact verification and the accuracy of individual registry fields are separate measures.

Sources