What does the :: in an IPv6 address mean?

The double colon represents one or more consecutive groups of all-zero hextets. It may appear only once in an address. This tool expands it back to the correct number of 0000 groups.

What is RFC 5952 compression?

RFC 5952 is the canonical text representation — lowercase hex, leading zeros dropped per group, and the longest run of two or more zero groups replaced by ::. The tool shows this canonical form alongside the full one.

Are addresses uploaded?

No. Parsing and formatting happen entirely in your browser.

IPv6 Expander

Expand a compressed IPv6 address to its full 8-group form.

Expand and canonicalise IPv6 addresses

Paste a compressed IPv6 address such as 2001:db8::1 and see its fully expanded eight-group form (2001:0db8:0000:0000:0000:0000:0000:0001), plus the canonical RFC 5952 compressed form.

The tool validates the address — only one :: is allowed, and each hextet must be 1–4 hex digits — so malformed input is flagged. Everything runs locally in your browser.