ActiveX is a very broad term that encompasses a number of different technologies developed by Microsoft. Many of these technologies are in some way related to the Internet and how we get around on the World Wide Web, and all of them are based on Microsoft’s Component Object Module (COM). Other than that, an accurate definition of ActiveX may take a little work…

What is ActiveX, anyway?

Although Microsoft introduced the term ActiveX in 1996, the different components upon which it is based were developed much earlier. It all began with the introduction of OLE (Object Linking and Embedding) for creating compound documents, in which objects created in different applications can be visually combined in a single container application. Within compound documents, active links between different programs can be maintained (like the automatic updating of Excel data embedded in a Word document when this spreadsheet data has been changed).

OLE and COM Technologies

The original idea behind OLE was to provide a means of creating documents containing different data types (like text, graphics, and multimedia) that could collectively be treated as a single document, while individually remaining separate for editing within their respective applications or incorporating into other documents. A natural next step would be to provide a more general methodology for allowing one application to provide services to another, and that’s exactly what Microsoft did with the development of COM (Component Object Model) technology. COM was introduced in OLE’s second release, OLE2. Therefore, even though COM was introduced as part of OLE, OLE is actually a subset of the more general COM technology.

But what is ActiveX, anyway?

We are now finally ready to define ActiveX. In short, ActiveX is name given in 1996 to the COM technology introduced as OLE2, even though this COM technology had very little to do with OLE or compound documents (other than being a more general means for software to provide services to other software). In other words, before 1996, OLE2 was synonymous with COM, and was therefore no longer considered an acronym for Object Linking and Embedding. To alleviate this confusion, Microsoft introduced a new name for the COM technology of OLE2 – ActiveX. Piece of cake, right?

ActiveX Controls

While the name ActiveX applies to the set of technologies described above, most people associate it with ActiveX Controls, a specific technology within that set. ActiveX controls are COM-based components for the desktop, called COM objects, which link desktop applications to each other and to the Web. These objects are pre-built component parts that follow a set of standardized rules governing how applications share information with one another. Programmers can develop ActiveX controls using several different programming languages, including C, C++, Visual Basic, and Java, thereby creating application building blocks that can be easily inserted into Web pages or other applications.

ActiveX controls are DLLs, so they can’t run on their own and need to be called from within a container application. The container application you’re probably most familiar with is Microsoft’s Web browser, Internet Explorer. ActiveX controls enable documents created in programs like Word or Excel to be viewed directly within Internet Explorer and other Web browsers.