Unique-Local address (ULA) is an IPv6 Unicast address type that is intended to be used privately within a site and unique among IPv6 nodes within one or more private networks. ULA is similar to the uniqueness of the Global Unicast address, but the context of its usage is not routable to the IPv6 Internet. ULA obsoleted the previous Site-Local Unicast address, which was similar to IPv4's RFC 1918 private use addresses.

The KAME Project has an online ULA generator that you can access here. This generator ensures the uniqueness of a ULA address. To read RFC4193 which defines ULA, click here.