# IPv6 Toolkit > Parse an IPv6 address or prefix to see its canonical (RFC 5952) and fully expanded forms, special-use classification, prefix math, an EUI-64 MAC if present, and its ip6.arpa reverse-DNS name. Runs entirely in your browser. - Tool: https://ronutz.com/en/tools/ipv6 - Family: Networking --- ## What it does Parse an IPv6 address or prefix and see it from every angle: its canonical short form and its fully expanded form, what kind of address it is, the prefix math for a block, a hardware MAC address if one is embedded in the interface identifier, and the reverse-DNS name that points back to it. Everything is computed in your browser. ## Canonical and expanded forms An IPv6 address is 128 bits, written as eight groups of four hexadecimal digits separated by colons. The same address can be written many ways, so RFC 5952 defines one canonical form: lowercase, with the leading zeros in each group removed and the single longest run of all-zero groups collapsed to `::`. The tool shows that canonical form and, alongside it, the fully expanded form with every group written out in full, which is the version you want when you need to see all 128 bits or line addresses up by column. For example, `2001:0db8:0000:0000:0000:0000:0000:0001` expands from, and canonicalizes to, `2001:db8::1`. ## Classification and prefix math Not every address is a normal public one. The tool classifies special-use ranges: the loopback `::1`, the unspecified address `::`, link-local addresses in `fe80::/10`, unique-local addresses in `fc00::/7` (RFC 4193), the documentation range `2001:db8::/32` reserved by RFC 3849, and IPv4-mapped addresses. When you give it a prefix, it computes the block's network address, its first and last address, and how many addresses it spans, the same arithmetic the CIDR tool does for IPv4 but on a 128-bit field. ## EUI-64 and reverse DNS Two extras fall out of the address. If the interface identifier was built from a network card's 48-bit MAC using the modified EUI-64 method (RFC 4291, Appendix A), the tool recovers that MAC, which is why privacy extensions exist to avoid leaking it. And it builds the `ip6.arpa` reverse-DNS name: the address's nibbles in reverse order, dot-separated, ending in `.ip6.arpa`, which is what a PTR lookup for the address uses. ## Using it Paste an IPv6 address to see its canonical and expanded forms, its classification, any embedded MAC, and its reverse-DNS name, or paste a prefix to add the block math. The parse is deterministic and reads only the address you give it. ## Standards and references - [RFC 4291 - IP Version 6 Addressing Architecture](https://www.rfc-editor.org/rfc/rfc4291) - text representation, address types/scopes, EUI-64 (Appendix A) - [RFC 5952 - A Recommendation for IPv6 Address Text Representation](https://www.rfc-editor.org/rfc/rfc5952) - canonical compression rules + mixed IPv4-mapped notation - [RFC 4193 - Unique Local IPv6 Unicast Addresses](https://www.rfc-editor.org/rfc/rfc4193) - the fc00::/7 unique-local classification - [RFC 3849 - IPv6 Address Prefix Reserved for Documentation](https://www.rfc-editor.org/rfc/rfc3849) - the 2001:db8::/32 documentation classification ## Related reading - [How IPv6 hosts get addresses: SLAAC and DHCPv6](https://ronutz.com/en/learn/ipv6-address-configuration.md): How an IPv6 host configures itself from link-local up, what router advertisements decide, and the difference between SLAAC, privacy addresses, and DHCPv6. - [IPv6 subnetting and the /64 boundary](https://ronutz.com/en/learn/ipv6-subnetting.md): Why IPv6 subnetting is about structure rather than scarcity, why a single subnet is almost always a /64, and how prefix delegation hands out address space. - [Neighbor Discovery: how IPv6 replaces ARP](https://ronutz.com/en/learn/ipv6-neighbor-discovery.md): How IPv6 finds neighbors on a link using ICMPv6 and multicast instead of broadcast ARP, the five Neighbor Discovery messages, and why broadcast is gone. - [Running IPv6 and IPv4 together: dual-stack and translation](https://ronutz.com/en/learn/ipv6-transition.md): How the internet bridges two incompatible address families: dual-stack, Happy Eyeballs, NAT64, and the IPv4-embedded addresses that make it work. - [Understanding IPv6 Addressing](https://ronutz.com/en/learn/ipv6-addressing.md): How a 128-bit IPv6 address is structured and written, the rules for compressing it canonically, what the address types and scopes mean, and how interface identifiers and reverse DNS work.