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. |
What Is the IP Address Validator?
The IP Address Validator checks whether the text you enter follows the correct syntax for an IPv4 or IPv6 address, and if it does, goes a step further by classifying it as private, loopback, link-local, multicast, or another special-use category. It is designed to give you an instant answer while you are writing server configuration files or application validation rules, so you can confirm on the spot whether the address notation you had in mind actually matches the standard.
Every check runs entirely inside your browser. The tool never sends the text you type to an external server, performs no DNS lookups, and does no WHOIS queries — it strictly validates the format of the string and classifies it according to well-established RFC definitions.
How to Validate an IP Address
- Type in the address Enter the IPv4 or IPv6 address you want to check in the input field. Leading and trailing spaces are trimmed automatically.
- Watch the result update live As you type, the address is analyzed in real time and a valid/invalid label appears immediately.
- Check the version and category For a valid address, the tool shows whether it is IPv4 or IPv6, along with its special-use classification, such as private or loopback.
- Read the reason for an invalid result If the format is wrong, a specific reason is shown, such as too few octets or a number outside the 0–255 range.
- Try the sample chips Click any sample chip to load a representative address instantly and see how its classification is determined.
Tips for getting more out of it
- 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.
When This Tool Comes in Handy
Testing a regular expression or validation library
Use it as a quick reference to confirm that your own validation logic correctly rejects edge cases such as leading zeros or out-of-range octets.
Sanity-checking connectivity before troubleshooting
Confirm whether a target address is private before you start debugging a connection, so you do not waste time chasing a host that was never meant to be reachable from the internet.
Understanding unfamiliar IPv6 notation
Paste in an IPv6 address that uses "::" compression or an IPv4-mapped form to see exactly how it expands and how it gets classified.
Picking a safe address for documentation
When writing a manual or sample code, check whether an address falls within the RFC 5737 documentation ranges so you avoid accidentally referencing a real, in-use address.
Glossary
- IPv4
- The traditional 32-bit IP address format, written as four decimal numbers from 0 to 255 separated by dots, such as 192.168.1.1.
- IPv6
- The next-generation 128-bit IP address format, written as eight groups of hexadecimal digits separated by colons, such as 2001:db8::1. It was designed to solve IPv4 address exhaustion.
- CIDR notation
- A way of expressing an address range by appending a slash and a bit count, such as /24, to an IP address. For example, 192.168.0.0/16 covers every address from 192.168.0.0 to 192.168.255.255.
- Octet
- Each of the four dot-separated parts of an IPv4 address, representing 8 bits and a value from 0 to 255.
- Hextet
- Each of the eight colon-separated parts of an IPv6 address, representing 16 bits written as a hexadecimal value from 0000 to ffff.
- Zero compression (::)
- A shorthand that collapses one or more consecutive groups of zeros in an IPv6 address into "::". It can be used only once within a single address.
- IPv4-mapped address
- A special IPv6 notation used to represent an IPv4 address, such as ::ffff:192.168.1.1, where the leading ffff marks the embedded IPv4 portion.
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.