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Private IP Range Checker
Check whether an IPv4 address falls inside a private (RFC 1918), loopback, link-local, or other reserved range, with the matching CIDR block and its typical use.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
| Range | CIDR | Use |
|---|---|---|
| 10.0.0.0–10.255.255.255 | 10.0.0.0/8 | Private (large networks) |
| 172.16.0.0–172.31.255.255 | 172.16.0.0/12 | Private (medium networks) |
| 192.168.0.0–192.168.255.255 | 192.168.0.0/16 | Private (home/small office) |
| 127.0.0.0–127.255.255.255 | 127.0.0.0/8 | Loopback |
| 169.254.0.0–169.254.255.255 | 169.254.0.0/16 | Link-local (APIPA) |
How the check works
- Type or paste an IPv4 address into the field.
- The tool tests it against the known private, loopback, link-local, multicast, and reserved CIDR blocks.
- It reports the matching range and CIDR, or confirms the address would be publicly routable.
FAQ
What are the three RFC 1918 private ranges?
10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — these are set aside by RFC 1918 for use inside private networks and are never routed on the public internet.
Why is 127.0.0.1 special?
The entire 127.0.0.0/8 block is the loopback range — traffic sent there always stays on the local machine, which is why "localhost" typically resolves to 127.0.0.1.
What is a link-local address used for?
A device automatically assigns itself an address in 169.254.0.0/16 (APIPA) when it can't reach a DHCP server, so it can still talk to other devices on the same local segment even without proper network configuration.
Quick lookup vs. a full subnet calculator
| Feature | This checker | Full subnet calculator |
|---|---|---|
| Instant private/reserved classification | ✓ | ✗ |
| Custom subnet mask/host range math | ✗ | ✓ |
Use this for a fast yes/no on whether an address is private; reach for a subnet calculator when you need actual network/host math.