I am currently transferring my website from using the client side flow version of facebook to using the server side flow (with the facebookauth helper) using Yesod and I am having issues getting the facebook plugin working. One of the interesting things I noticed is that the redirect_uri that Yesod outputs for my website is https://graph.facebook.com/oauth/authorize?client_id= <REMOVED>&redirect_uri=http%3a%2f%2flocalhost%2fauth%2fpage%2ffacebook&scope=userEmail%2cuserName%2cuserPasswordHash%2cuserCountryCode%2cuserActivated" Now the way I read this, the field in your facebook app should be localhost/auth/page/faceboook/ however putting this gives the error that redirect_uri is not the same as specified in the application, so I changed this to the same as the destination route which is defined in YesodAuth as loginDest _ = RootR (so in this case its just localhost), however when doing this I get an error (from facebook) stating "Invalid Arguments" (I retrieve a HTML page with the following in the body) <body><h1>Invalid Arguments</h1><ul><li>No input found</li></ul></body> Is there a trivial example lying around implementing simple facebook login using Yesod