Networking
IPv6 Validator & Notation Tool
Validate IPv6 syntax, expand collapsed colons, and inspect address scopes.
Reading the Address Scope
The scope tells you where an address is valid — the single most useful fact when debugging IPv6 connectivity. A link-local address (fe80::/10) only exists between two devices on the same link and never routes; a unique local address (fc00::/7) is the IPv6 equivalent of RFC 1918 private space; a global unicast address (2000::/3) is what the wider internet sees.
The canonical output follows RFC 5952: lowercase hexadecimal, leading zeros in each hextet removed, and at most one "::" — placed where it suppresses the most zeros. Two addresses that look different can be the same address, which is why validating them here beats comparing strings by eye.
Reading an IPv6 Address Without Guessing
An IPv6 address is eight groups of 16 bits written in hexadecimal. Two shortcuts make it readable: leading zeros inside a group can be dropped (0db8 becomes db8), and one run of all-zero groups can be replaced by a double colon. The double colon may appear only once, because two of them would make it impossible to know how many zero groups each one stands for.
The scope of an address matters as much as its syntax. Addresses starting with fe80 are link-local and never leave the local network segment, fc00::/7 is reserved for unique local addresses, and 2000::/3 is where global unicast addresses live. If a pasted address is rejected here, the usual causes are a stray character outside 0-9 and a-f, a group longer than four digits, or a second double colon.
How the Network Math Works
- Parses 128-bit hextet syntax and normalizes representation per RFC 5952.
Worked Network Example
Common Questions
What is RFC 5952?
The official IETF standard specifying canonical text formatting for IPv6.
What does a leading "::" represent?
The double colon replaces one or more contiguous groups of zero hextets. RFC 5952 allows it only once per address to stay unambiguous, so expanders reconstruct the full 8-group form from right to left.
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