Rangdom

Expand an IPv6 address to its full form

Paste any IPv6 address — short or long — and get the fully expanded form: exactly 8 groups of 4 lowercase hex digits, with leading zeros restored and any :: replaced by the correct number of all-zero groups. The fixed-width form is what you want for sorting, diffing, and reliable string comparison. 2001:db8::1 becomes 2001:0db8:0000:0000:0000:0000:0000:0001, and :: becomes the all-zero address.

What is accepted

Input in either notation is accepted: 8 colon-separated groups, or fewer groups with exactly one :: standing in for the omitted zero groups, with 1–4 hex digits per group. Round-tripping a valid address through expand → compress → expand is stable. Out of scope and rejected with an inline error rather than guessed: embedded IPv4 dotted notation (::ffff:192.168.0.1), zone IDs (%eth0), CIDR prefixes, and multiple addresses. Everything runs in your browser — nothing is uploaded.

Related tools