AJAX request from one subdomain to another subdomain, but on the same domain

I know that you can't do cross-domain ajax requests unless you use a 'proxy' one server.

However, if I did an ajax request from server1.example.com to server2.example, would that not work, even though it's on the same doma开发者_StackOverflow中文版in of example.com?

I'm pretty sure sites such as YouTube do ajax requests to different servers. such as a request from youtube.com to vs1022.youtube.com etc.

Any clarification on this would be superb. Thank you for your time.

server1.example.com and server2.example.com considered as cross domain for AJAX request.

You would need to set the header Access-Control-Allow-Origin: * at server side.

Access-Control-Allow-Origin: * header should be formed with set of whitelist maintained by web service provider, unless web services validate requests using auth tokens.