Active Server Pages (ASP) is Microsoft's first server-side script engine for dynamically-generated web pages. It was initially marketed as an add-on to Internet Information Services (IIS) via the Windows NT 4.0 Option Pack, but has been included as a free component of Windows Server since the initial release of Windows 2000 Server. Programming ASP websites is made easier by various built-in objects. Each object corresponds to a group of frequently-used functionality useful for creating dynamic web pages. In ASP 2.0 there are six such built-in objects: Application, ASPError, Request, Response, Server, and Session. Session, for example, is a cookie-based session object that maintains variables from page to page. Web pages with the ".asp" or ".aspx" extensions use ASP, although some Web sites disguise their choice of scripting language for security purposes.

Most ASP pages are written in VBScript, but any other Active Scripting engine can be selected instead by using the @Language directive or the <script language="language" runat="server"> syntax. JScript (Microsoft's implementation of ECMAScript) is the other language that is usually available. PerlScript (a derivative of Perl) and others are available as third-party installable Active Scripting engines.