Selenium WebDriver Drivers

WebDriver is the name of the key interface against which tests should be written, but there are several implementations. These include:

HtmlUnit Driver
This is currently the fastest and most lightweight implementation of WebDriver. As the name suggests, this is based on HtmlUnit. HtmlUnit is a java based implementation of a WebBrowser without a GUI. For any language binding (other than java) the Selenium Server is required to use this driver.

Firefox Driver
Controls the Firefox browser using a Firefox plugin. The Firefox Profile that is used is stripped down from what is installed on the machine to only include the Selenium WebDriver.xpi (plugin). A few settings are also changed by default (see the source to see which ones) Firefox Driver is capable of being run and is tested on Windows, Mac, Linux. Currently on versions 3.6, 10, latest - 1, latest

Internet Explorer Driver
This driver is controlled by a .dll and is thus only available on Windows OS. Each Selenium release has it’s core functionality tested against versions 6, 7 and 8 on XP, and 9 on Windows7.