Unique Local Address
Even so, IPv6 does have a ‘private’ IP space that’s not allowed on the internet. These addresses are called unique local addresses.
These IPs are routable, but only within your own network. They are not routable over the internet.
These may be a good choice if you want to try using IPv6 in your network, but haven’t been assigned a range from your service provider or RIR yet.
They can also be good for labs, or if you want to have an isolated network for security.