CIDR aggregator
Paste a messy allow-list and get the tidiest set of blocks that covers exactly the same addresses.
One per line, or separated by commas. Comments after # are ignored.
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What does aggregating actually do?
It merges entries that overlap or sit next to each other, then splits each merged run into the fewest CIDR blocks that cover it exactly — no more and no fewer addresses than you started with. Two neighbouring /25 blocks become a single /24.
Why did my two blocks not merge?
A CIDR block has to start on a multiple of its own size. 10.0.0.0/24 and 10.0.1.0/24 merge into 10.0.0.0/23 because the pair is aligned, but 10.0.1.0/24 and 10.0.2.0/24 cannot, even though they touch.
What can I paste in?
CIDR blocks (10.0.0.0/8), bare addresses, an IPv4 netmask (10.0.0.0 255.0.0.0) and dashed ranges (10.0.0.1 - 10.0.0.50). IPv4 and IPv6 can be mixed; they are aggregated separately.