Same thing for the search engine. The search engine doesn’t care, it serves full urls based on domain names, not IP addresses thus it is up to the user to have IPv6 or not. What I do know is that their bot seems to pick/prefer IPv6 to index a website if the website has it, I believe the bot isn’t probably even aware of what IP stack it’s using - like any other program it does DNS resolution, gets whatever IP is available and fetches the website.
Same thing for the search engine. The search engine doesn’t care, it serves full urls based on domain names, not IP addresses thus it is up to the user to have IPv6 or not. What I do know is that their bot seems to pick/prefer IPv6 to index a website if the website has it, I believe the bot isn’t probably even aware of what IP stack it’s using - like any other program it does DNS resolution, gets whatever IP is available and fetches the website.