IPv6 Address Expander and Compressor - SimeonOnSecurity

NOTE: This tool runs entirely in your browser with client-side JavaScript. The address you enter is expanded locally and is never transmitted, logged, or stored.

IPv6 address

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Enter an address to expand it.

Reading IPv6

Eight groups of four hex digits. Each group is 16 bits, so a full address is 128 bits. The double colon stands in for one run of all-zero groups and may appear only once.
Compression is a display choice. 2001:db8::1 and 2001:0db8:0000:0000:0000:0000:0000:0001 are the same address. Expanding shows the true bit pattern, which is what you need when two addresses look different but are not.
The prefix matters more than the rest. Firewall and routing decisions act on the prefix, so two addresses in the same /64 are neighbours no matter how the host portion is written.