Why Class C subnets matter for link diversity
A Class C subnet is the first three sections of an IPv4 address (e.g. 192.168.1.x) - sites hosted on the same subnet are often on the same physical server or the same hosting account. Paste a list of domains (competitor backlink sources, or your own link-building targets) and this tool resolves each one's IP and flags which domains share a subnet, which can indicate they are hosted together rather than being truly independent sites.
Why this check matters for backlink quality assessment
A backlink profile made up mostly of sites on the same few subnets can look like a private blog network (PBN) rather than organically earned links from independent sites - diversifying hosting is one signal (among many) of a more natural link profile, which is why checking subnet overlap is a useful step when auditing either your own backlink profile or evaluating a batch of potential link sources.
Why sharing a subnet isn't proof of anything on its own
Many legitimate, unrelated websites share hosting infrastructure, especially on popular shared hosts or cloud platforms, where thousands of unrelated sites commonly sit on the same IP ranges. Seeing a shared subnet is one data point worth factoring into a broader assessment, not a definitive finding that two sites are secretly connected.
What to do when several domains share a subnet
If a notable portion of a backlink list shares subnets, it's worth investigating those specific domains further - checking whether they also share similar site structures, templates, or ownership details (through WHOIS, where available) - rather than treating the subnet overlap alone as conclusive proof of a manipulative link scheme.