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developer validator

CIDR Overlap Checker

Check whether two IPv4/IPv6 CIDR blocks overlap—runs entirely client-side.

Results

Paste input and validate locally.
Status
Ready when you validate.
Details
Ready when you validate.
Overlap?
Ready when you validate.
Family
Ready when you validate.
Overlap start
Ready when you validate.
Overlap end
Ready when you validate.

Rules & checks

Parses IPv4 and IPv6 CIDRs and requires the same family for both.

Computes overlap range when present.

Runs fully client-side/offline; no CIDRs leave the page.

When to use it

  • Avoid conflicting firewall or security group rules
  • Sanity-check overlapping VPC/VNET CIDRs before peering
  • Validate user-entered allowlists in admin panels

Tips

  • Keep both CIDRs in the same protocol (IPv4 or IPv6)
  • Normalize CIDRs to reduce accidental overlaps

Examples

Overlap

  • 10.0.0.0/24 vs 10.0.0.128/25 -> overlap

No overlap

  • 10.0.0.0/24 vs 10.0.1.0/24 -> no overlap

IPv6 overlap

  • 2001:db8::/64 vs 2001:db8::/65 -> overlap

FAQs

Is any data stored or sent?
No. Everything runs locally and clears on refresh.
Can I compare more than two?
Compare pairs here; for bulk overlap use multiple checks.

Related validators

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CIDR Validator

Validate IPv4/IPv6 CIDR blocks and view the normalized network address.

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IP Range Validator

Validate start/end IP ranges (IPv4 or IPv6) and check ordering.

Format-only; does not test reachability or routing behavior.