IPv6 Expand/Compress — Address Converter

IPv6 is the next-generation protocol with a 128-bit address space (2¹²⁸ addresses). Addresses are written as 8 groups of 16-bit values in hexadecimal.

RFC 5952 compression rules

Leading zeros within a group are removed: 0DB8 → DB8;
The longest run of consecutive all-zero groups is replaced with ::;
Only one :: is allowed per address.

Frequently Asked Questions

What is the difference between default IPv6 compression and RFC 5952 compression?

Basic compression may remove leading zeros, but RFC 5952 introduces strict rules: replace with :: only the longest consecutive sequence of all-zero groups; if two sequences are equal in length, choose the leftmost one; and never use :: more than once in an address. Our tool follows RFC 5952 strictly, ensuring compatibility with any network equipment.
Can I use the converter to verify IPv6 addresses found in firewall logs?

Yes, that is one of the key use cases. Paste the address from the log into the input field, select the "Expand" mode, and you will get the full 128-bit notation with all groups visible. This makes it easy to compare addresses, spot errors in filter rules, and correctly configure access policies.
Why is ::ffff:192.168.1.1 considered an IPv4-mapped IPv6 address?

This address type is used to represent IPv4 nodes in an IPv6 environment. The first 80 bits are zero, the next 16 bits are all ones (ffff), and the last 32 bits contain the IPv4 address. Our converter correctly recognizes such addresses, expands them to their full form (0000:0000:0000:0000:0000:ffff:c0a8:0101), and labels them as "IPv4-mapped" — useful when migrating from IPv4 to IPv6.