CIDR
CIDR Merger
Normalize and merge IPv4 CIDR lists into a minimal set.
Input
Provide a multiline list of IPv4 CIDRs.
Processes up to 5000 lines.
All calculations run locally in your browser.
Output
Minimal merged CIDR set
Valid input
0
Output
0
Reduction
0.0%
What
CIDR Merger definition
CIDR merging removes duplicate/contained ranges and combines adjacent blocks when possible.
Cases
Use Cases
1
Simplify firewall ACL rules
2
Remove duplicate network ranges
3
Clean large CIDR inventories
How To
How to merge CIDR lists
Paste CIDRs and reduce them to the minimal representation.
1
Paste CIDRs
Enter one IPv4 CIDR per line.
2
Run merge
Start merging to normalize, deduplicate, and combine ranges.
3
Review output
Check reduced output count and copy merged CIDRs.
Knowledge
Understanding CIDR merging
Why merge CIDRs
Reducing rule count makes ACLs easier to review and maintain.
Normalization
Normalizing to network address form enables reliable comparisons.
Containment reduction
Subnets fully covered by broader ranges can be eliminated safely.
Adjacent supernet merge
Two sibling networks can merge only if they are contiguous and aligned.
Policy caution
Always verify merged output still matches your intended access policy.
FAQ
CIDR Merger FAQ
What input format is supported?
Only IPv4 CIDR notation (for example, 10.0.0.0/24).
How are duplicates handled?
Duplicate normalized CIDRs are removed automatically.
How are contained ranges handled?
If a larger block fully contains a smaller one, the smaller one is dropped.
When can adjacent ranges merge?
Adjacent blocks with the same prefix merge only when supernet boundaries align.
How are bad lines reported?
Each invalid line is reported with line number and content.
Is there an input cap?
Yes. A line limit protects browser resources.
Does it support IPv6?
Not in this version. IPv4 only.
Is data uploaded anywhere?
No. Merging runs entirely in-browser.