Loading page
About this tool
Expand a shortened IPv6 address to its full form.
The IPv6 Expander rewrites a compressed IPv6 address into its full uncompressed form: it replaces the :: shorthand with the exact number of zero groups needed to reach eight, then left-pads every group to four hex digits. Enter 2001:db8::1 and you get 2001:0db8:0000:0000:0000:0000:0000:0001. It is for network engineers, developers and anyone who needs the canonical long form because a device, config file or comparison refuses to accept the shortened notation.
Open IPv6 Expander on AltFTool — it loads instantly in your browser.
Type or paste a shortened address into the 'IPv6 address' field under Inputs; it opens pre-filled with 2001:db8::1. Text with no colon in it leaves the Result at an em dash under the caption 'Enter an IPv6 address'.
The Result updates live as you type — there is no expand button. The :: shorthand is refilled with zero groups and every group is padded to four hex digits, so 2001:db8::1 becomes 2001:0db8:0000:0000:0000:0000:0000:0001 with the caption 'expanded'.
Press Copy to put the title, your IPv6 address and the expanded Result on the clipboard (the button reads Copied for a moment), Download to save that same text as ipv6-expander.txt, or Reset to restore the default address.
Works whether the double colon sits at the start, the middle or the end, filling exactly the number of zero groups required to reach eight.
Restores dropped leading zeros so db8 becomes 0db8, which is what makes two differently written addresses directly comparable as strings.
The full form updates with each keystroke, so a mistyped group is obvious immediately rather than after a submit step.
It means writing all eight 16-bit groups in full, each as four hexadecimal digits — 32 hex digits and seven colons in total. Compression drops leading zeros within a group and replaces one run of all-zero groups with ::, and expansion puts both back.
2001:0db8:0000:0000:0000:0000:0000:0001. The :: stands in for five all-zero groups here, because the written groups (2001, db8 and 1) account for three of the eight, and db8 is padded to 0db8.
Because it means 'as many zero groups as needed to make eight', and two of them would be ambiguous — there would be no way to tell how many zeros belong to each run. A single :: always has exactly one valid expansion.
No. The compressed and expanded forms are the same 128-bit address, and both are valid IPv6 notation under RFC 4291. The expanded form is simply unambiguous for text comparison and for systems that do not parse the shorthand.