Why this tool is useful
Use aggregation to shorten firewall allowlists, route fixtures and network documentation while preserving the exact union of the submitted address ranges.
Developer & Data · runs locally
IPv4 CIDR Aggregator
Merge overlapping or adjacent IPv4 addresses and CIDR blocks into the smallest exact set of route prefixes without adding outside addresses.
Ready. Your working data stays in this browser.
How it works
Every input becomes an unsigned start/end range, overlapping and adjacent ranges are merged, then each merged interval is decomposed into aligned power-of-two CIDR blocks.
Practical example
Two neighboring /25 blocks covering 192.0.2.0 through 192.0.2.255 collapse to one 192.0.2.0/24, while an unrelated single address remains a /32.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.