What this IP address checker tells you
Not every IP address is meant for the public internet. The IETF and IANA reserve dozens of blocks for special purposes: private networks, loopback, carrier-grade NAT, documentation examples, multicast and more. This tool validates the format of the address you enter and checks it against the IANA IPv4 and IPv6 Special-Purpose Address Registries, so you know immediately whether an address is public, private or something else, and which RFC defines it.
Why it matters
- Troubleshooting: a
169.254.x.xaddress means your device did not get a DHCP lease. A WAN address in100.64.0.0/10means your ISP uses carrier-grade NAT, so port forwarding will not work. - Security: applications that fetch URLs should block private, loopback and link-local destinations to prevent server-side request forgery (SSRF).
- Configuration: confirm a range is safe to use internally before assigning it to a LAN or VPN.
IPv4 and IPv6 special-purpose ranges
| Block | Purpose | RFC | Public? |
|---|---|---|---|
| 0.0.0.0/8 | "This network" | RFC 791 | No |
| 10.0.0.0/8 | Private-Use | RFC 1918 | No |
| 100.64.0.0/10 | Shared Address Space (CGNAT) | RFC 6598 | No |
| 127.0.0.0/8 | Loopback | RFC 1122 | No |
| 169.254.0.0/16 | Link-Local (APIPA) | RFC 3927 | No |
| 172.16.0.0/12 | Private-Use | RFC 1918 | No |
| 192.0.0.0/24 | IETF Protocol Assignments | RFC 6890 | No |
| 192.0.2.0/24 | Documentation (TEST-NET-1) | RFC 5737 | No |
| 192.31.196.0/24 | AS112-v4 | RFC 7535 | Yes |
| 192.52.193.0/24 | AMT | RFC 7450 | Yes |
| 192.88.99.0/24 | Deprecated 6to4 Relay Anycast | RFC 7526 | No |
| 192.168.0.0/16 | Private-Use | RFC 1918 | No |
| 192.175.48.0/24 | Direct Delegation AS112 | RFC 7534 | Yes |
| 198.18.0.0/15 | Benchmarking | RFC 2544 | No |
| 198.51.100.0/24 | Documentation (TEST-NET-2) | RFC 5737 | No |
| 203.0.113.0/24 | Documentation (TEST-NET-3) | RFC 5737 | No |
| 224.0.0.0/4 | Multicast | RFC 5771 | No |
| 240.0.0.0/4 | Reserved (Class E) | RFC 1112 | No |
| 255.255.255.255/32 | Limited Broadcast | RFC 919 | No |
| ::/128 | Unspecified Address | RFC 4291 | No |
| ::1/128 | Loopback | RFC 4291 | No |
| ::ffff:0:0/96 | IPv4-Mapped IPv6 | RFC 4291 | No |
| 64:ff9b::/96 | IPv4/IPv6 Translation (NAT64) | RFC 6052 | Yes |
| 64:ff9b:1::/48 | Local-Use IPv4/IPv6 Translation | RFC 8215 | No |
| 100::/64 | Discard-Only | RFC 6666 | No |
| 2001::/32 | Teredo | RFC 4380 | Yes |
| 2001:2::/48 | Benchmarking | RFC 5180 | No |
| 2001:db8::/32 | Documentation | RFC 3849 | No |
| 2001:20::/28 | ORCHIDv2 | RFC 7343 | Yes |
| 2002::/16 | 6to4 | RFC 3056 | No |
| 3fff::/20 | Documentation | RFC 9637 | No |
| fc00::/7 | Unique Local (ULA) | RFC 4193 | No |
| fe80::/10 | Link-Local Unicast | RFC 4291 | No |
| ff00::/8 | Multicast | RFC 4291 | No |
Everything else in IPv4, and the 2000::/3 global unicast block in IPv6, is ordinary public address space allocated by the regional internet registries. Learn the difference between public and private IPs.
Common IP format mistakes
- Numbers above 255: each IPv4 octet is a single byte, so
10.0.0.256is invalid. - Leading zeros:
010.001.001.001is ambiguous because some software reads it as octal, so modern parsers reject it. - Multiple
::in IPv6: the shorthand can appear only once, otherwise the address cannot be expanded unambiguously. - Missing octets:
192.168.1is not a complete address, even though some tools expand it.
Frequently asked questions
Is 192.168.x.x a public IP?
No. 192.168.0.0/16 is a private range defined in RFC 1918 and is never routed on the internet.
What is the 100.64.x.x range?
Shared address space for carrier-grade NAT (RFC 6598). If your router's WAN IP is in this range, your ISP shares one public IPv4 address among many customers.
Can I use documentation addresses on my network?
Avoid it. 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 and 2001:db8::/32 exist so that examples never collide with real networks.