Implementing the same original policy?

SOP is implemented in the browser (client side) as far as I know.

I have played with the console before and I am submitting the xmlhttprequest from the wiki to reddit to restore its json file.

x = new XMLHttprequest();
x.open("GET","any reddit page + .json");
x.send();
x.response;

      

        
        
        
      

    

Somehow it went through and I get the data.

I tried this on another page, it is SOP blocked as I assumed. Now I'm confused.

Is SOP supported by the browser? how does basic SOP work?

I used chrome.