What is the difference between ASP.Net AJAX ScriptManager and Ajax control ToolkitScriptManager?

ASP.Net Ajax is a framework released by Microsoft to develop Ajax enabled web application. One has to write a lot of javascript code to do an asynchronous communication with the server using XmlHttpRequest object previously. Since Ajax has become one of the mostly widely used technologies because of the user experience it provides. Microsoft released its own framework called ASP.Net Ajax which helps to build Ajax application easily and quickly.

The ASP.Net Ajax framework has a control called ScriptManager which manages the asynchronous communication between the client and server. This control will actually emit a javascript code file which has various methods to do Ajax call using XmlHttpRequest object. After releasing ASP.Net Ajax framework, Microsoft with the participation of community developers released an open source toolkit called Ajax control toolkit which has some set of Ajax enabled controls that can be used readily in an ASP.Net application. This toolkit also released its own version of ScriptManager control called Ajax control ToolkitScriptManager which does exactly the same thing as ASP.Net Ajax ScriptManager but with some additional advantages.

Let's see some of the differences between ASP.Net AJAX ScriptManager and Ajax control ToolkitScriptManager.

Both the script manager differ in the way they render the javascript behaviour files to the client side. ToolkitScriptManager uses a technique called script combining to download the scripts and improves the performance.

Recomended reading,
http://blogs.msdn.com/delay/archive/2007/06/11/script-combining-made-easy-overview-of-the-ajax-control-toolkit-s-toolkitscriptmanager.aspx