IP Address Validator — Check IPv4/IPv6 Format & Detect Private Ranges (Free)
Instantly check whether a string is a valid IPv4 or IPv6 address and automatically classify it as private, loopback, link-local, multicast, or public. Runs entirely in your browser — no external lookups, pure format validation.
Special-Use IP Address Ranges
A reference table of well-known IP address ranges whose purpose is defined by RFC standards.
| Category | IPv4 range | IPv6 range | Description |
|---|---|---|---|
| Unspecified address | 0.0.0.0 | :: | A special address indicating that no address has been assigned yet. |
| Loopback address | 127.0.0.0/8 | ::1 | Refers to the local host itself; packets never leave the device. |
| Private address | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 | fc00::/7 | Used on closed networks such as a corporate LAN and never routed directly on the internet. |
| Link-local address | 169.254.0.0/16 | fe80::/10 | Auto-assigned and valid only on the local segment; routers never forward it. |
| Multicast address | 224.0.0.0/4 | ff00::/8 | Delivers to multiple destinations at once rather than identifying a single host. |
| Broadcast address | 255.255.255.255 | — | A special address used to send to every host on the local network at once. |
| Documentation address | 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 | — | Reserved by RFC 5737 for use in manuals and sample code. |
| Reserved address | 240.0.0.0/4 | — | Reserved by IANA for future use; not used in ordinary traffic today. |
Tips
- This tool never makes a network request — everything runs in your browser, doing pure format checking and RFC-based classification.
- Useful for double-checking the IP ranges you plan to use before writing server config files or application validation rules.
- Private addresses (like 192.168.x.x) cannot be reached directly from the internet, so this is the first thing to verify when troubleshooting internal connectivity.
- Leading zeros like "01" are interpreted ambiguously by many systems (some treat them as octal), so this tool intentionally rejects them.
FAQ
Side Note — Why "Private" IP Addresses Cannot Reach the Internet
The IPv4 private address ranges (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16) were defined by RFC 1918 back in 1996. At the time, the number of networked devices in businesses and homes was exploding, and assigning one of the roughly 4.3 billion IPv4 addresses to every single device was simply not sustainable. The solution was to carve out ranges meant only for internal use, with ISPs worldwide agreeing that internet routers would never carry routes to these destinations — a simple convention that helped stretch a limited resource much further.
IPv6 has an equivalent concept: the unique local address range, defined as fc00::/7, which plays the same role as private IPv4 space. With 128 bits and roughly 3.4×10^38 possible addresses, IPv6 has no realistic exhaustion problem, yet the designers still carved out a non-globally-routed range for traffic meant to stay entirely inside an organization — a deliberate design choice worth noting.
Link-local addresses (169.254.0.0/16 for IPv4, fe80::/10 for IPv6) act as a fallback: a device assigns one to itself automatically when no DHCP server can be found. Many people have seen two directly cabled computers end up with 169.254.x.x addresses — a telltale sign that network configuration was never completed.