My ISP gives me a /56, and many provide a /48. That's huge. We are 4 people, each with 2-3 devices, and frequent guests on our wifi. Pretty sure such a database would be highly unreliable. And some ISPs rotate the allocated subnet, some make it static. You would probably have the same level of reliability with an IPv4 database currently ("IP visitor from a niche US-based ISP" is probably the same user, and you could dedupe by browser and other data).

And then jurisdictions such as the EU, Canada and California would consider the IP address to be PII, and it would be illegal to contribute to such a database.

Again, there are much more easier ways to track people on the Internet.

With the rotating IPv4 you at least have the possibility to make yourself more anonymous. IPv6 takes that decision away from you.

> You would probably have the same level of reliability with an IPv4 database currently

That is... a lie. The selling point of today's internet is that you are anonymous.

Also I don't know which "easier ways to track people" you mean.

>IPv6 takes that decision away from you

No, it doesn't. Your ISP is the one who can take that decision away from you. I have Google Fiber, and my public IPv4 address has not changed in around six months, while my IPv6 block has changed twice in that same time. This is despite replacing my router and several multi-hour power outages. I believe the only reliable way to get a new IPv4 address is to call support.

Precisely one of the things I hate about ipv6. I want the anonymity of cgnat, thanks.