IPv4 to IPv6 Converter
Convert any IPv4 address into its IPv6-mapped notation and related representations, entirely in your browser.
IPv4 to IPv6 notation
Enter an IPv4 address and get its IPv4-mapped IPv6 form (RFC 4291) plus the matching 6to4 prefix. The conversion happens entirely on this page.
About IPv4 to IPv6 Converter
The most common reason to convert an IPv4 address to IPv6 is the IPv4-mapped IPv6 address, defined in RFC 4291. It has the form ::ffff:a.b.c.d and works by placing the original 32-bit IPv4 address in the last 32 bits, preceded by 16 one-bits (ffff) and 80 zero-bits. Dual-stack hosts use this representation so that an IPv6 socket can accept and log IPv4 connections - which is why an IPv4 visitor often shows up in server logs as something like ::ffff:203.0.113.42.
This converter shows several equivalent forms of that address so you can use whichever your system expects: the readable dotted form (::ffff:203.0.113.42), the pure hexadecimal-group form (::ffff:cb00:712a), and the fully expanded 128-bit address with every group written out. Seeing all three side by side makes it easy to match the exact string a firewall rule, ACL, or log parser is looking for.
As a bonus the tool derives the 6to4 prefix - 2002 followed by the IPv4 address in hexadecimal, giving a /48 such as 2002:cb00:712a::/48. 6to4 was an early transition mechanism for tunnelling IPv6 over IPv4 networks and is now deprecated for new deployments, but the derivation is still handy for reading or documenting legacy 6to4 addressing.
Everything runs client-side. The conversion is pure arithmetic performed in your browser with JavaScript, so the address you type is never uploaded, logged, or sent to any server - useful when you are working with internal or sensitive addresses.
How to use it
- 1Type an IPv4 address in standard dotted-quad form (for example 203.0.113.42).
- 2Read the IPv4-mapped result in both dotted notation (::ffff:203.0.113.42) and hexadecimal-group notation (::ffff:cb00:712a).
- 3Copy the fully expanded 128-bit form when you need the address written out with no abbreviation.
- 4Use the derived 6to4 /48 prefix if you are working with legacy 6to4 addressing.
- 5Paste the representation your firewall, ACL, or logging system expects.
Common use cases
- -Making sense of dual-stack server logs where IPv4 clients appear as ::ffff: addresses.
- -Writing firewall rules or access-control lists that must match the IPv4-mapped form of an address.
- -Understanding exactly how a specific IPv4 address is embedded inside a 128-bit IPv6 address.
- -Documenting or teaching IPv4 and IPv6 address representation with concrete, correct examples.
- -Normalising addresses to a single form before comparing or storing them.
Frequently asked questions
- What is an IPv4-mapped IPv6 address?
- An IPv4-mapped IPv6 address has the form ::ffff:a.b.c.d and embeds a 32-bit IPv4 address in the last 32 bits of an IPv6 address (RFC 4291). It lets an IPv6 socket represent an IPv4 endpoint on a dual-stack host.
- How do you convert an IPv4 address to IPv6?
- Prefix the 32-bit IPv4 value with 80 zero-bits and 16 one-bits - written as ::ffff: followed by the address. For example 203.0.113.42 becomes ::ffff:203.0.113.42, which this tool produces instantly.
- Is ::ffff:192.0.2.1 the same as 192.0.2.1?
- It represents the same IPv4 host inside an IPv6 context, but it is not a natively routable IPv6 address. The mapped form only has meaning on a dual-stack system; on the public IPv6 internet the host still uses its real IPv4 address.
- What is the 6to4 prefix shown by this tool?
- The 6to4 prefix is 2002 followed by the IPv4 address encoded in hexadecimal, producing a /48 such as 2002:cb00:712a::/48. 6to4 is a deprecated IPv6 transition mechanism, included here for reading and documenting legacy addresses.
- Does this converter send my address anywhere?
- No. The conversion runs entirely in your browser using local JavaScript, so the IPv4 address you enter is never uploaded, stored, or transmitted to any server.