IETester Browser Compatibility Check for Internet Explorer Versions from 5.5 to 10 IETester is a free (both for personal and professional usage) WebBrowser that allows you to have the rendering and javascript engines of IE10 preview, IE9, IE8, IE7 IE 6 and IE5.5 on Windows 7, Vista and XP, as well as the installed IE in the same process. IETester is embedding multiple versions of Internet Explorer rendering engine (called Trident) into one process.Trident is an ActiveX control, thus a COM object, and can be embedded into any application. IEtester is using this logic to embed engines, but hooks the COM functions to redirect calls to custom IE versions instead of the standard one installed on the OS.