An ActiveX® plug-in is a computer program that operate inside of and interacts with a program such as Microsoft® Windows® Internet Explorer®. Such a plug-in allows browsers and other utilities to perform certain functions, such as displaying videos or games. Plug-ins may also be used to add features to a program that were not present in the original installation. They are downloaded and installed to your computer via your Internet connection. Unveiled in 1996, the ActiveX® plug-in was the successor to two similar types of technologies, called the "component object model" and "object linking and embedding."
An ActiveX® plug-in can be created using a variety of programming languages, though ActiveX® itself is not a programming language. Instead, languages such as C++ and Java are used to create these plug-ins. It is also possible for plug-ins to interact and integrate with the HTML programming language.
Programs in the Windows® operating system, in addition to web browsers, have the ability to use ActiveX® plug-ins and controls. These programs include, but are not limited to, Microsoft® Office™, Microsoft's productivity software suite; and Windows® Media Player®. ActiveX® plug-ins help these programs share information with both the web and with other programs on the same computer.
ActiveX® plug-ins are only available to computers running on the Windows® operating system. This causes sites that rely heavily on ActiveX® technology and plug-ins to display improperly on operating systems such as Mac OS X® and Linux®. Mozilla® Firefox® does not support ActiveX®, although third-party plug-ins enabling the technology have been released. Firefox® instead uses different types of plug-ins and extensions to perform many of the same functions as ActiveX®.
Users have the ability to enable or disable ActiveX® plug-ins when using the Internet Explorer® web browser. If enabled, users can also specify different levels of security. Internet Explorer® can prompt the user when an ActiveX® plug-in needs to be installed, can download all plug-ins automatically, or can be set to only download plug-ins from secure sites.
By design, ActiveX® plug-ins have full administrative access to every aspect of the Windows® operating system. This makes the technology one of the primary ways that malicious programs such as spyware and adware are downloaded to a computer from the web. It is for this reason that browsers that support ActiveX® give users the ability to disable the technology at their discretion. This is also one of the primary reasons cited by the development team of Mozilla® Firefox® as to why that browser does not openly support the technology.