Class C IP Checker - Free Bulk Domain Check

A Class C IP checker shows which IPv4 range each of your domains sits in, so you can spot sites that share the same hosting block. Paste one domain per line, run the check, and get every domain's IP address, its Class C range, and a count of how many ranges are shared.

What Is a Class C IP Address?

A Class C IP address is an IPv4 address in the range 192.0.0.0 to 223.255.255.255, where the first three numbers (octets) identify the network and the last number identifies the host. The default subnet mask is 255.255.255.0, which gives 256 addresses per block and 254 usable hosts.

In SEO and link building, "Class C" has become shorthand for the first three octets of an address, such as 203.0.113.x. Two domains whose IPs start with the same three numbers sit in the same /24 block. That usually means the same hosting company, and often the same server or the same account.

Why people check it

Link builders, owners of multi-site portfolios and anyone auditing a private blog network want to know how many of their sites sit together. A cluster of sites in one block is an easy footprint to spot. Whether it matters depends on your goal, and the sections below explain how to judge that.

Class C versus private ranges

You may also see "Class C" used for private addresses like 192.168.1.x. Those are internal network addresses and do not appear on public websites. This tool reports public IPv4 addresses for domains, so a result starting with 192.168 would not be a real hosting result. If you need to convert a block like 203.0.113.0/24 into its first and last address, the CIDR to IP range converter does that in one step.

How to Use the Class C IP Checker

You can check a whole list of domains in under a minute with a single text box and one button.

1. Open the tool and find the text area labeled for domains. The placeholder shows the format: example.com, google.com and github.com, each on its own line.
2. Paste or type your domains, one per line. You can include http:// or https:// prefixes, and the tool strips them for you.
3. Leave out paths and extra notes. A bare domain such as example.com gives the cleanest result.
4. Submit the form with the check button.
5. Read the four summary counts at the top: Domains, Unique IPs, Unique Class C and Shared Class C.
6. If any ranges are shared, read the highlighted list of ranges, each shown as a range followed by .x and the number of domains in it.
7. Scroll to the results table to see every domain with its IP address and Class C range, then use the link at the bottom to start a new check.

Worked Example: Five Domains, Three Ranges

Suppose you paste five domains from a link portfolio and the tool resolves them like this (these are documentation-range IPs used for illustration).

The summary would read: 5 Domains, 5 Unique IPs, 3 Unique Class C and 1 Shared Class C. The shared list would show 203.0.113.x (3).

Here is the reasoning. All five IP addresses are different, so a simple IP check looks clean. But three sites share the first three octets, so 60% of your list sits in one block. If these were meant to look like independent sources, you would want to move at least two of them or replace them with sites from other hosts.

How Do You Read the Results?

Each number in the summary answers a specific question about how spread out your domains are.

• Domains: how many valid, unique domains were checked. Duplicates and invalid lines are not counted.
• Unique IPs: how many different IPv4 addresses the domains resolved to. If this is lower than Domains, some sites share an exact IP.
• Unique Class C: how many different three-octet ranges appear. The closer this number is to Domains, the more spread out your list is.
• Shared Class C: how many ranges contain more than one domain. Zero means no overlaps.

What good and poor results look like

A strong result has Unique Class C equal to Domains and Shared Class C at 0. A mixed result has a few ranges with two domains each, which is common when sites use the same popular host. A poor result has one range holding a large share of the list, as in the example above.

How to fix a shared range

Look at the table to find which domains share the range. Then move one or more of them to a different hosting provider, or choose different sites when you are still selecting link sources. After the change, run the list again to confirm the range count dropped. To see what else lives on a shared address, try a reverse IP lookup.

Who Uses a Class C Checker and When?

This tool is most useful when you manage many domains or evaluate many link sources at once.

• Link builders: paste the domains that link to you, or the domains you plan to approach, and see how clustered they are.
• Agency and portfolio owners: check whether client or personal sites ended up on one hosting block after a migration.
• Site auditors: review a list of referring domains from a backlink export and flag groups that come from one network.
• Network and hosting admins: confirm how a set of hostnames maps to address blocks before planning changes.
• Site buyers: check whether a set of sites for sale share infrastructure, which tells you something about who runs them.

If you want more than the range, such as location and provider for each address, send the same IPs to the bulk IP lookup. For a single domain, the domain to IP tool is faster.

Best Practices, Common Mistakes and Troubleshooting

Most surprising results come from how the input is written or from how hosting works.

Enter clean domains

Use one domain per line and no commas or spaces between entries. A line that is not a valid domain or URL is skipped and listed as an error under the summary, with the reason beside it. If every line is invalid, the tool tells you no valid domains were supplied.

Duplicates are removed

If example.com appears twice, or once as example.com and once as https://example.com, the second entry is left out of the counts and flagged as a duplicate. This keeps a repeated domain from creating a fake shared range.

"Unavailable" in the IP column

When no public IPv4 address can be verified for a domain, the IP shows as Unavailable and the domain is left out of the range counts. Common causes are a domain that does not exist, a domain that only has an IPv6 record, or a temporary DNS failure. Check the domain's records with an A record lookup, and run it again later if the DNS looks fine.

Look at the provider, not just the range

Two ranges that differ in the third octet can still belong to one company. After you find your ranges, an ASN lookup shows which network owns each address, which is a better test of true hosting diversity.

Do not chase a perfect score

Google's Search Central documentation does not list Class C diversity as a ranking factor. Treat the result as a footprint check: it tells you how connected your sites look to anyone who inspects them, not what a search engine will do with them. Links from relevant, trusted sites matter far more than the address block they sit in.

Limitations and Accuracy Notes

The checker reports what each domain's DNS currently points to, and that has a few boundaries you should know about.

• Each domain is matched to one public IPv4 address. A domain with several A records is represented by the first one returned, so the result is a snapshot, not a full list.
• Sites behind a content delivery network or a shared proxy often resolve to the provider's ranges. Many unrelated sites can then appear in one range even though they are hosted separately.
• IPv6 addresses are not grouped. Only IPv4 addresses are assigned to a Class C range.
• The range is the first three octets only. It does not show the real size of the network that owns the address, which can be larger or smaller than a /24.
• DNS changes over time, so results can differ if a site moves hosts or changes its records.

For other lookups that complement this one, such as DNS records, name servers and address tools, browse the full Network and IP tools collection.

Check Your Domain List Now

Paste your domains into the box above, one per line, and you will see within seconds how many unique IPs and Class C ranges you really have, and which ranges are shared. Fix the clusters you find, then run the list again to confirm your hosting is as spread out as you intended.