I am working on a web app which requires a user to login to their reddit account and according to https://github.com/reddit/reddit/wiki/OAuth2#retrieving-the-access-token I need to send a POST request to https://www.reddit.com/api/v1/access_token with some parameters. I am currently running the server from localhost and I keep getting the error:
XMLHttpRequest cannot load https://www.reddit.com/api/v1/access_token. Request header field Access-Control-Allow-Origin is not allowed by Access-Control-Allow-Headers.
I was struggling with this same issue and figured out that I need to register my app as "Installed" instead of "Web". This will make the authorization redirect with the bearer token instead of the code.