IPv4/IPv6 Converter

IPv4 192.0.2.1 → ::ffff:192.0.2.1.

How it works

• Parsed the 32-bit IPv4 address.
• Prepended the 0xffff marker for the IPv4-mapped form and the all-zero prefix for the compatible form.
• Placed the address in the 6to4 prefix 2002::/16.

• IPv4-compatible addresses are deprecated but still recognised.
• A general IPv6 address is never coerced into an IPv4 address.

Methodology

1. Detect the address family with strict parsers (dotted-quad first, then IPv6).
2. For IPv4, place the 32-bit value in the mapped, compatible and 6to4 prefixes.
3. For IPv6, split into eight groups, compress the longest zero run, expand, and serialise the 128-bit value as a big integer.
4. Refuse to coerce a general IPv6 address into IPv4.

Usage

1. Choose a conversion mode (or leave it on Auto).
2. Enter an IPv4 or IPv6 address.
3. Read or copy the converted forms.

Examples

These are examples, not current values: they use fixed inputs, while the interactive tool computes live results in your browser.

IPv4 to its IPv6 forms

{
  "address": "192.0.2.1",
  "mode": "ipv4-to-ipv6"
}

Normalise a compressed IPv6

{
  "address": "2001:db8::1",
  "mode": "ipv6-normalize"
}

Recover IPv4 from an IPv4-mapped address

{
  "address": "::ffff:192.0.2.1",
  "mode": "ipv6-to-ipv4"
}

Limitations

Three ways to embed IPv4

IPv6 has several address forms that carry an IPv4 address in their low 32 bits. The IPv4-mapped form (::ffff:0:0/96) represents an IPv4 node on a dual-stack host, 6to4 (2002::/16) encodes an IPv4 address as the tunnel endpoint, and the deprecated IPv4-compatible form (::/96) was an early transition mechanism.

Text compression is separate from the address itself: :: may replace the longest run of zero groups once, and the converter always round-trips the address through its 128-bit integer value so the notation and the value never disagree.