Illegal redirect_uri trying to authenticate with spotify api

var request = require('request'); // "Request" library

var client_id = 'id'; // Your client id
var client_secret = 'secret'; // Your secret
var redirect_uri = 'http://localhost:8888/callback/'; // Your redirect u
 

I'm trying to authenticate with the spotify api but I'm getting a 400 error saying Illegal redirect_uri. My redirect URL on spotify dashboard is IDENTICAL so I'm not sure sure why this error is showing.