Offline mode means users can still use the app when network connection is lost. This can be done by caching API data so that it can be used later and a network service to detect when your network is lost or available.  To make your app work in offline mode, you need to create an offline manager service which stores requests made during that time so that we can send the requests when network is available.  For this , ionic has the ionic/storage and ionic-native/network modules. The Network module provides onConnect() and onDisconnect() events which can be used to track network changes.