IPv4 to IPv6 Converter - Mapped, 6to4 & Mixed

There is no single “the IPv6 version” of an IPv4 address, and that is the confusion this tool exists to clear up. An IPv4 address is 32 bits; an IPv6 address is 128. The extra 96 bits have to be filled with something, and the three formats here fill them differently for three different purposes. Picking the wrong one is the usual mistake — so it helps to know what each is actually for before you copy it.

The only one you will meet day to day is the IPv4-mapped address. When a program opens a dual-stack socket and an IPv4 client connects, the operating system hands the code an address like ::ffff:192.168.1.1. The ::ffff:prefix is a flag that says “the last 32 bits are really an IPv4 address”, letting one code path handle both protocols. You see these in server logs and access-control lists far more often than you generate them by hand.

The conversion itself is not a lookup or an approximation — it is a direct rewrite of the same 32 bits. Each octet becomes two hex digits: 192 is c0, 168 is a8, 1 is 01, and 1 is 01. Group those into two 16-bit blocks and you get c0a8 and 0101, which is why 192.168.1.1 maps to ::ffff:c0a8:101. Nothing is invented; the dotted-decimal and the hex are the same number in two scripts.

The one subtlety is formatting. RFC 5952, the standard for writing IPv6 addresses, says leading zeros inside each group must be dropped: 0101 is written 101, 0808becomes 808, and a zero group is just 0. This tool applies that rule, so the output matches what a router, a log parser, or another engineer’s tooling will produce. It matters because a naive converter that emits ::ffff:c0a8:0101creates a string that is equal in value but unequal as text — and text comparisons are exactly how addresses get matched in config files and firewall rules.

The most common real use is reading logs. A dual-stack web server will record an IPv4 visitor as ::ffff:203.0.113.5, and if you are grepping access logs or writing a rule to match that client, you need to recognise that the ::ffff: form and the plain 203.0.113.5are the same host. The second use is sanity-checking a firewall or ACL entry: paste the IPv4 address, confirm the mapped form matches what your rule expects, and move on. Both are quick lookups, which is why the whole thing runs locally with no network round trip — the address you type never leaves the page.

Note: These outputs are representations of an address, not interface configuration. The mapped form is how software refers to an IPv4 peer; the 6to4 and IPv4-compatible forms are historical. Verify against your own routing and DNS before relying on any of them in a live system.