How to use the IPv6 Expander and Compressor
- 1. Paste an addressAny valid form: 2001:db8::1, with /64, with %zone or with an IPv4 tail.
- 2. ConvertPress the button to see both forms.
- 3. Use the detailsCopy the full form, the compressed form or the ip6.arpa name.
How IPv6 is written
An IPv6 address is 128 bits written as eight groups of four hex digits separated by colons. Two rules make it shorter: leading zeros in a group can be dropped (0db8 → db8), and one run of all-zero groups can be replaced by ::. RFC 5952 sets the standard short form: lowercase, shortest possible, and :: used for the longest run of two or more zero groups.
Worked example: 2001:db8::1 expands to 2001:0db8:0000:0000:0000:0000:0000:0001. The :: stood for five zero groups. The tool also identifies it as a documentation-only address (2001:db8::/32 is reserved for examples) and builds its reverse DNS name ending in ip6.arpa.
Address types and prefixes
- ::1 is loopback, like 127.0.0.1.
- fe80::/10 is link-local, valid only on one network segment and often written with a zone like %eth0.
- fc00::/7 is unique local, the IPv6 version of private ranges.
- 2000::/3 is global unicast, the public internet.
- ff00::/8 is multicast.
Add a prefix length such as /64 and the tool shows the network address and the first and last address in that block. A /64, the standard size for one subnet, contains 2⁶⁴ addresses. Only one :: is allowed per address, because two would be ambiguous; the tool explains invalid input instead of guessing. Look up common services' ports with the port numbers reference, or pull addresses out of logs with the IOC extractor.
Frequently asked questions
Is 2001:DB8::1 the same as 2001:db8::1?
Yes. Hex is case-insensitive, but RFC 5952 recommends lowercase.
What about ::ffff:192.0.2.1?
That is an IPv4-mapped address. The tool accepts the dotted part and shows the IPv4 address.
Is the IPv6 Expander and Compressor free?
Yes, the IPv6 Expander and Compressor is free. The first time you see your first result, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.