@Leonardo-Augusto said: OAuthException Googling the error code shows this: In FB App you have to assign an IP Site/ App Domain. Facebook matches this url with the url of the request where it came from. You can not assign localhost or You have to enter the IP address your server. Also if it is rails then call the site with your-ip:3000 instead of localhost:3000; I use Enter the same IP address in IP of the site and APP Domain in your FB APP Settings. Edit: Maybe a better answer: http://stackoverflow.com/questions/4691782/facebook-api-error-191