Is it possible to use the API to make a web client without hosting an intermediary server

I am developing a WebGL Go board, and I would like to add OGS support; however, when I try to access the API from a browser, I get an “Cross-Origin Request Blocked” error. I would like to know if I am doing something wrong or if it is simply impossible to use the API to make a web client, and if it is impossible, is there a way to make it possible?