This error fires on this method, App.initilizeApp(). To solve this you need to, import firebase from “firebase/app”; export const initializeLoginFramework = !firebase.apps.length ? firebase.initializeApp(appConfig) : firebase.app() The reason behind this is that firebase can only be initialized once. This method checks to see whether there it’s been initialized already, and only initializes it if it has been. If not, it just returns the initialized firebase app.