Class C IP Checker
This free class C IP checker resolves up to 40 domains and groups them by their /24 address range, the first three numbers of the IPv4 address. It flags ranges and single addresses shared by more than one domain, which usually means the sites are hosted together. Use it to audit a backlink list or a group of your own sites.
Class C IP Checker
Domain and Server
About this tool
Sites hosted on the same server or in the same small block of addresses are often run by the same people. Link buyers and private blog network operators know this, and so do search engines: dozens of links from domains in one class C range look like one source, not many. Checking the ranges in a backlink list is a quick way to see whether its diversity is real.
The checker resolves each domain's A records and takes the first three numbers of the address, for example 203.0.113 from 203.0.113.10, which is the /24 block that the old IPv4 class system called a class C network. Domains in the same block are grouped and counted, and domains on exactly the same address are flagged separately. Everything comes from live DNS; nothing is fetched from the sites.
Sharing a range proves hosting proximity, not ownership. Shared hosting, cloud providers and CDNs put thousands of unrelated sites in the same blocks, and Cloudflare alone puts millions behind a few ranges, so a shared range behind a CDN means nothing. Treat the result as one signal to combine with WHOIS data, link patterns and content, not as a verdict.
Frequently asked questions
What is a class C IP address?
In the original IPv4 scheme, class C networks held 256 addresses that shared their first three numbers, such as 203.0.113.0 to 203.0.113.255. The classes were retired in 1993, but SEO tools still use "class C" to mean that /24 block, because sites in it are often on the same hosting network.
Why do links from the same class C range matter for SEO?
Many links from one range suggest one owner or one hosting account, so search engines may count them as a single source rather than independent votes, and a pattern of cross-linked sites in one range is a classic footprint of a link network. Links from genuinely different networks carry more weight.
My domains share a range because they are on the same host. Is that bad?
Not for ranking. Google has said that shared hosting is normal and not a penalty. It only becomes a problem when the sites exist mainly to link to each other. If you run several legitimate sites, hosting them together is fine; just do not build their link profiles out of each other.
Why do sites behind Cloudflare all look like they share a range?
Because the DNS points at Cloudflare's addresses, not at the real servers. Cloudflare serves millions of sites from a small set of ranges, so a shared range there says nothing about ownership. The tool cannot see through a CDN; the domain hosting checker tells you when one is in front.