It works for me. Care to show me a screenshot?

The host (assuming the same host) is responding with a different website when accessed via IPv4 vs IPv6.

  $ curl -4s http://kairos.xyz/ | grep title
      <title>Kairos</title>

  $ curl -6s http://kairos.xyz/ | grep title
  <title>Welcome to nginx on Debian!</title>

  $ host kairos.xyz
  kairos.xyz has address 107.161.29.121
  kairos.xyz has IPv6 address 2604:180:0:a54::24d9

Thanks, I found the problem. I thought that with Nginx, Ipv6 would just work but I had to add

    listen 80;
    listen [::]:80;

to my server block.

"Welcome to nginx on Debian!

If you see this page, the nginx web server is successfully installed and working on Debian. Further configuration is required.

For online documentation and support please refer to nginx.org

Please use the reportbug tool to report bugs in the nginx package with Debian. However, check existing bug reports before reporting a new bug.

Thank you for using debian and nginx."

I meant here: http://kairos.xyz/

When I make a request from another IP, it gives me the right page.

" (...) Try...

Who is Richard Stallman? define bravado 10 USD to EUR RFC 2460 generate username help - about"

This is so strange. If I fetch the page from http://archive.is I get the same default Nginx page

http://archive.is/AxHFV

the only thing I can think off right now is that the http "Host" header field is not sent. I have several sites on the same server and Nginx is used as a reverse proxy and uses the Host field to redirect traffic to different ports.

You should really consider using multiple server blocks instead of relying on the Host field.

I do. Nginx does the matching using the Host field http://nginx.org/en/docs/http/ngx_http_core_module.html#serv...

Hmm, I could've sworn that server_name doesn't rely on the Host header. My mistake.

I also get the Nginx default page when I click on your link from my iPhone. I'd take a screenshot but not sure how to link that from here.