BYTETOOLS

CIDR Aggregator

Aggregate a list of IPs and CIDR blocks into the minimal covering set. Merges overlapping and adjacent IPv4 ranges into clean summary routes — 100% offline.

5
Input entries
3
Aggregated blocks
769
Addresses covered

Minimal covering CIDR set

10.0.0.5/32
192.168.0.0/23
192.168.2.0/24

What is the CIDR Aggregator?

The CIDR Aggregator turns a long, messy list of IPv4 addresses and CIDR blocks into the smallest equivalent set of blocks.

  • Merges overlapping, duplicate and adjacent ranges in one pass
  • Splits merged ranges into the minimal set of aligned CIDR blocks
  • Accepts bare IPs, CIDR blocks and blocks with host bits set (10.0.0.7/24)
  • Reports skipped invalid lines instead of failing silently
  • Shows total addresses covered plus before/after block counts
  • 100% client-side — sensitive IP lists never leave your machine

How to use the CIDR Aggregator

  1. 1

    Paste IPv4 addresses and CIDR blocks, one per line — bare IPs count as /32.

  2. 2

    The tool merges overlapping and adjacent ranges automatically as you type.

  3. 3

    Check the stats for input entries versus aggregated block count.

  4. 4

    Copy the minimal CIDR set or download it as a text file.

About the CIDR Aggregator

The CIDR Aggregator turns a long, messy list of IPv4 addresses and CIDR blocks into the smallest equivalent set of blocks. It normalises every line to an integer range, sorts them, merges everything that overlaps or sits adjacent, and then re-splits each merged range into properly aligned CIDR blocks.

Use it to shrink firewall rule sets, summarise routing tables, dedupe allowlists and blocklists exported from different systems, or verify that two /25s really do collapse into one /24. The before/after counts show exactly how much the list shrank, and invalid lines are reported rather than silently dropped.

Everything runs 100% locally in your browser using 32-bit integer math — your IP lists are never uploaded, which matters when they describe your internal network or security rules.

Frequently asked questions

What is CIDR aggregation (route summarization)?

It is replacing many small IP blocks with fewer, larger blocks that cover exactly the same addresses. For example 192.168.0.0/24 and 192.168.1.0/24 aggregate into 192.168.0.0/23. Routers and firewalls process shorter lists faster, and configs get much easier to audit.

When can two subnets be merged into one?

Two blocks of the same size can merge only if they are adjacent and the combined range starts on a boundary aligned to the larger size. 192.168.0.0/24 + 192.168.1.0/24 merge into a /23, but 192.168.1.0/24 + 192.168.2.0/24 do not, because a /23 cannot start at .1.0.

Does aggregation change which IPs are covered?

No. This tool only merges ranges that are genuinely contiguous or overlapping, so the output covers exactly the same addresses as the input — never more, never fewer. The 'addresses covered' stat lets you verify that the total stayed the same.

Why did my list not get any smaller?

If your blocks are scattered with gaps between them, nothing can merge without covering addresses you did not list. Aggregation only helps when ranges touch or overlap. The tool still dedupes exact duplicates and blocks contained inside bigger ones.

Does this work with IPv6?

Not yet — this tool is IPv4-only, using exact 32-bit arithmetic. IPv6 lines are reported as invalid rather than mishandled. For IPv6 prefix math, use the IPv6 subnet calculator.

Is my IP list uploaded anywhere?

No. Parsing, merging and splitting all happen in your browser with JavaScript. Firewall rules and internal ranges are sensitive, so the tool was built to work fully offline — nothing is transmitted or logged.

Related tools