Basic aim of making Castbin is to make it easy to create casts. Be it for demonstrating your website or showing a test case. Anyone with a modern browser should be able to make a good looking screencast in few minutes
Making screencast usually involves installing a software, knowing how to use it correctly. Editing the cast and uploading it in correct format. Castbin tries to get rid of all this complexity and allows you to get embed code to use on your website or share it with someone in few minutes.
Like any new way of doing things, there are some challenges though. You need to use Google Chrome for recording the cast. Although, using Firefox might work, it is not well tested. For playback, though you can use any modern browser i.e. Chrome, Firefox and IE11+.
For more information see Frequently Asked Questions.