Visualize CIDR ranges and subnet allocations on an interactive IP address space map with overlap detection.
CIDR Network Visualizer converts a list of network prefixes into an interactive address-space map. Each block is positioned by the addresses it covers, making containment and overlap visible across proposed or existing allocations. It is especially useful when a flat list hides that one subnet sits inside another. The usual mistake is reading a larger slash number as a larger network. For IPv4, increasing the prefix length by one halves the block, so /25 is smaller than /24. Internal address plans remain in the browser and are not uploaded.
A concrete input and expected output from the current implementation.
Input
192.168.1.0/24 192.168.1.128/25
Expected output
Two plotted blocks. 192.168.1.0/24 spans 192.168.1.0 through 192.168.1.255, totaling 256 addresses. 192.168.1.128/25 spans 192.168.1.128 through 192.168.1.255, totaling 128 addresses. An overlap is detected across those 128 addresses, with the /25 fully contained in the /24.
An IPv4 /24 leaves eight address bits variable, giving 2^8 = 256 addresses. A /25 leaves seven bits variable, giving 128 addresses, and the .128 boundary places all of them inside the upper half of this /24.
For an IPv4 entry, a prefix length p fixes the leading p bits and leaves 32 - p bits variable. That defines 2^(32 - p) consecutive addresses on a matching boundary. The map represents that complete interval, so a shorter prefix covers more address space and appears larger than a longer prefix.
Two CIDR entries overlap whenever their numeric address intervals share at least one address. This includes full containment, such as a /25 inside a /24, as well as duplicate prefixes. The visualization exposes the shared space, but the overlap marker does not decide whether that relationship is intentional, permitted, or operationally harmful.
No. It means the CIDRs describe at least one common address. A parent allocation and one of its child subnets overlap by design, as do an aggregate route and its more-specific route. If the entries represent networks that must be independently allocated, however, the same marker identifies a conflict worth investigating.
IPv4 prefix lengths count fixed leading bits, not available host bits. Moving from /24 to /25 fixes one additional bit and leaves half as many combinations for the remaining bits. The blocks therefore contain 256 and 128 addresses respectively. Their visual sizes describe address-space coverage, not traffic, utilization, or device count.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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