IPv6 to IPv4 Converter

IPv6 to IPv4 converter extracts the embedded IPv4 address from IPv4-mapped IPv6 addresses per RFC 4291 §2.5.5.2. IPv4-mapped addresses use the ::ffff:0:0/96 prefix — 80 zero bits, followed by 16 all-one bits (0xFFFF), followed by a 32-bit IPv4 address. When an IPv6 address arrives in this format, the tool strips the ::ffff: prefix and converts the remaining two four-digit hex groups back to dotted-decimal IPv4 notation. Native IPv6 addresses with no embedded IPv4 payload return an incompatible result — the IPv6 address space (2¹²⁸) is vastly larger than IPv4 (2³²), so no general one-to-one mapping exists.

IPv4-mapped IPv6 addresses appear in two valid notations. Both are accepted — the tool detects the format automatically and returns the same extracted IPv4 address regardless of which form is entered.

RFC 4291 reserves the ::ffff:0:0/96 block within the IPv6 address space specifically for representing IPv4 addresses. The /96 prefix means only the last 32 bits vary — exactly the size of an IPv4 address — placing all 2³² IPv4 addresses within this range.

For hex notation — ::ffff:c0a8:0101 — the tool strips ::ffff:, removes the colon separator, and processes the remaining 8-character hex string as four two-character pairs: c0 → 192, a8 → 168, 01 → 1, 01 → 1 → result: 192.168.1.1.

For dotted-decimal notation — ::ffff:192.168.1.1 — the IPv4 portion after ::ffff: is already in the correct format and is returned directly without further conversion.

All extraction runs in the browser using JavaScript — no address data leaves the device.

Web server log normalization. nginx and Apache on dual-stack servers log IPv4 client connections as ::ffff:x.x.x.x when bound to an IPv6 socket. Extracting the IPv4 address allows existing log parsers, analytics pipelines, and rate-limit systems to process entries without modifying their IPv4-only regex patterns.

Application-layer debugging. A Python or Go application using AF_INET6 sockets receives client addresses in ::ffff:c0a8:0101 notation. Converting those addresses to dotted-decimal confirms which IPv4 client is connecting and allows comparison against expected source ranges or ACL entries.

Bulk packet capture analysis. A sysadmin reviewing a dual-stack pcap file has extracted a list of ::ffff: source addresses using Wireshark. Pasting the list into bulk mode converts all entries at once, producing a clean IPv4 list for cross-referencing against firewall rules or threat intelligence feeds.