IP Address Validator & Type Checker (IPv4, IPv6)
Check whether IPv4 and IPv6 addresses are valid and what kind each is: private, public, loopback, link-local, CGNAT, documentation, multicast or reserved, with its class.
| Address | Valid | Version | Type | Public | Class | Notes |
|---|---|---|---|---|---|---|
| 192.168.1.1 | Yes | IPv4 | Private (RFC 1918) | No | C | |
| 8.8.8.8 | Yes | IPv4 | Public | Yes | A | |
| 100.72.10.5 | Yes | IPv4 | Shared address space / carrier-grade NAT (RFC 6598) | No | A | |
| 2001:db8::1 | Yes | IPv6 | Documentation (RFC 3849) | No | — | |
| fe80::1%eth0 | Yes | IPv6 | Link-local | No | — | zone %eth0 |
| 256.1.1.1 | No | — | — | — | — | 256 is larger than 255 |
Paste one address or a whole list to see which are valid and what each one is. The checker reads IPv4 strictly — four numbers from 0 to 255, with no leading zeros, since some software reads 010 as octal 8 — and IPv6 in all its shortened forms, including embedded IPv4 and zone indexes. Every valid address is matched against the IANA special-purpose registries: private (RFC 1918), carrier-grade NAT, loopback, link-local, documentation, benchmarking, unique-local, multicast, reserved or public. IPv4 addresses also show their historical class and default mask.
How to use this tool
- Paste IP addresses, one per line or separated by commas.
- Read the verdict for a single address, or the counts for a list.
- Use the table for each address: valid or not, version, type, whether it is publicly routable, and its class.
- Fix the invalid entries using the reason shown, such as a number above 255 or a misplaced "::".
Formula
IPv4: a.b.c.d with each part 0–255; IPv6: eight 16-bit hex groups, one "::" for a run of zero groups; type = the most specific IANA block that contains the address
Private IPv4 blocks are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16; 100.64.0.0/10 is shared space used by carrier-grade NAT; 169.254.0.0/16 is link-local; 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24 are for documentation. In IPv6, fc00::/7 is unique-local (private), fe80::/10 link-local and 2000::/3 global unicast. Classes: A = first number 0–127, B 128–191, C 192–223, D 224–239 (multicast), E 240–255.
Example
192.168.1.1 is valid, private (RFC 1918) and class C with a default mask of 255.255.255.0 — the typical home router address. 8.8.8.8 is public and class A. 256.1.1.1 is invalid because 256 is larger than 255. 2001:0db8:0000:0000:0000:0000:0000:0001 is valid; it shortens to 2001:db8::1 and is reserved for documentation.
Frequently asked questions
Is 100.64.x.x a private address?
Not in the RFC 1918 sense. 100.64.0.0/10 is shared address space for carrier-grade NAT: your provider gives it to your router and translates it to a public address. Seeing it on your router's WAN side means you do not have your own public IPv4 address.
Why is 192.168.01.1 marked invalid?
A leading zero is ambiguous: some programs (and browsers in URLs) read 01 as octal, others as decimal. Strict parsers, including modern Python, reject it. Write 192.168.1.1.
What does a % at the end of an IPv6 address mean?
It is a zone index, such as %eth0 or %12, telling the computer which network interface to use. Link-local addresses (fe80::/10) exist on every interface, so the zone picks one. It is not part of the address itself.
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/ip-address-validator/
Cite or embed this tool
kakaoCalc. (2026, November 8). IP Address Validator & Type Checker (IPv4, IPv6). https://kakao.mobile/tools/ip-address-validator/
“IP Address Validator & Type Checker (IPv4, IPv6).” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/ip-address-validator/.
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