Failed loading 'app/view/Viewport.js', please verify that the file exists
Trying to get MVC to work and you're getting "Failed loading 'app/view/Viewport.js', please verify that the file exists" as an error? The solution: add the following line to your Ext.application config; autoCreateViewport: false, its that simple! So now a basic config for an Ext.application should look like; Ext.application({ name: 'AM', autoCreateViewport: false, appFolder: 'app', launch: function() { Ext.create('Ext.container.Viewport', { layout: 'fit', items: [ { xtype: 'panel', title: 'Users', html : 'List of users will go here' } ] }); } }); For more information on the MVC in Extjs4 look no further than the official guide http://docs.sencha.com/ext-js/4-0/#/guide/application_architecture