As the Web has evolved from primarily textual display of information to the use of multimedia to display information, the number of file formats has increased dramatically. Browsers acquire the ability to display media in various formats through the use of plug-in modules. Plug-ins are software programs that extend the capabilities of a Web browser like Microsoft Internet Explorer or Netscape Communicator to load or execute a file in some other format than HTML. For example, plug-ins permit the browser to play audio files or view movies from within the browser. Plug-ins enhance the capabilities of a Web browser by making even more features available than the browser already offers. So Web browsers commonly provide support for use of plug-in modules. Plug-in modules embed features such as real-time synchronized audio and video, virtual reality browsing, and inline document viewing into the browser.

Browsers usually come with a number of plug-ins already installed, but occasionally it is necessary to install a new plug-in or update an existing one. In most cases a link is provided to a website offering the needed plug-in. To install the plug-in, click on the link for the plug-in and follow the directions to install the plug-in to the browser. It may be necessary to restart the browser program after installing the plug-in. Some common (essential) browser plug-ins include the following modules:

• Apple QuickTime - The Apple QuickTime plug-in lets you experience QuickTime animation, music, MIDI, audio, video, and virtual reality panoramas and objects directly in a Web page.
• Adobe Acrobat Reader – PDF files are the most reliable, efficient, and effective way to share information electronically, and Acrobat Reader displays PDF files.
• Macromedia Flash Player – Flash Player is used to experience animation and entertainment on the Web. Flash is the Web standard for vector graphics and animation.
• Shockwave by Macromedia – The Shockwave plug-in is used to experience quality interactive games, multimedia, graphics, and streaming audio on the World Wide Web.
• RealPlayer by RealNetworks - RealPlayer plays streaming audio, video, and animation files on the World Wide Web.