An IPv6 unique local address (ULA) prefix is for addressing within a site or interconnected private sites, not for normal routing on the public Internet. IPv6 ULA Generator creates random /48 prefixes starting with fd in your browser.
Get two example prefixes
Set How many to 2 and click Generate. Under ULA prefixes (/48), you should see two lines shaped like fdxx:xxxx:xxxx::/48, where each x is a hexadecimal digit. The exact values change each run. Copy takes both lines; Download saves ipv6-ula.txt.
The 40 random bits make a collision less likely, but this tool does not consult other networks or reserve a prefix. Record which prefix you actually deploy, especially if two networks may later connect. A ULA is not an access-control rule: configure routing and firewall policy separately, and do not assume the prefix alone keeps traffic private.
Where your input goes
Processing runs in your browser. The tool does not upload your input to ilham.dev.
Related guide
For more background, read Network Debugging Notes.
Questions you might have
- What is the difference between fc00::/7 and fd00::/8?
- The whole range is fc00::/7. The fd00::/8 half is where the 40-bit global ID is generated locally rather than assigned by a registry, which is the practical choice.