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CIDR tools

Split, aggregate, contains, exclude, range to CIDR and CIDR to range.

Runs in your browser; nothing is uploaded

Lists use one complete CIDR per line. Range input uses start - end. Results stop at 4,096 blocks. Everything runs in your browser.

Choose an operation and enter a CIDR or range.

Exports contain every output block. CSV fields are quoted and spreadsheet formula prefixes are neutralised.

CIDR operations

Split divides one block into equal smaller blocks. Aggregate finds the minimal cover of overlapping or adjacent inputs. Contains checks whether an address or whole block sits inside another. Exclude subtracts blocks that lie inside a parent. Range to CIDRs covers inclusive endpoints with the fewest aligned blocks; CIDR to range shows its first and last addresses.

Rules and limits

Every address and prefix must match a complete strict format. IPv4 and IPv6 are kept separate. Scoped IPv6 is refused for network math. A split or exclusion that would produce more than 4,096 blocks returns an error. The page shows up to 1,000 result rows, while CSV and JSON include the full result.

Privacy

Calculations run in your browser. A short set of inputs can be shared in a URL fragment that is not sent to the server. Nothing is uploaded.

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