Apache is a public-domain open source Web server distributed under an “open source” license. It is a freely available on the web, making it easy to adapt the source code for specific server needs. Apache also offers a large library of add-ons that can assist in customizing the server even further. Features can range from authentication schemes to server-side programming language support. Instead of only implementing a specific architecture, Apache provides a variety of Multi Processing Modules (MPM) to adapt to different infrastructures. Although Apache is not platform independent, different versions is available to suit almost all platforms.