CIDR Summarizer / Aggregator

Paste a list of IPv4 prefixes or addresses, one per line, and this finds the smallest set of CIDR blocks that covers all of them — the same route-summarization math a router does when aggregating a routing table. Overlapping, duplicate, and out-of-order input is all handled.

Provided as-is, with no warranty of any kind. This runs entirely in your browser as a convenience tool, not a certified reference — always double-check results before relying on them for anything important, especially production changes. See the full disclaimer.