[tolien]

Right, but is Google doing this with the information they get from your IP address or something else entirely? Is it just coincidence that your IP address corresponds to your ISP’s office which happens to be relatively local?

With loose enough permissions your browser has a geolocation API that, depending on your device, will be a hell of a lot more accurate (if you have Wi-Fi hardware it can use that to work out where it is relative to the known locations of the SSIDs it can see, or straight-out use GPS).

None of this has anything to do with IPv6 - you give away some location information with your username and profile on this very site, for example.

[easrng]

I believe Google has their own IP geolocation database, likely seeded from all their apps that have location access because the location given at the bottom of the search results pages is always far more accurate than any other IP geolocater I've seen and there are others on my WiFi network who use Google services with location.