Snap-in, in general, refers to an object that can be attached to another object and that will then function as part of the whole. Hardware snap-ins usually fit this description. In reference to software applications, a snap-in is a program designed to function as a modular component of another application. Examples of snap-ins include Shym Technology 's PKEnable snap-in security system for use in e-mail and Web applications, and Novell's ZENworks for Desktops 3 Cluster Snap-in, which contains the program to support workstation inventory in a cluster environment. iMaximize claims that their snap-in products make it possible for any user who can operate a word processing program to create a feature-rich Web site in an hour.
Snap-ins are the basic components of Microsoft's Management Console (MMC). The MMC snap-ins are the actual management tools; the console - sometimes referred to as a "tools host" - is simply a framework into which the snap-ins are added. Within the MMC environment - which is similar to Windows explorer - the user selects from a list of all installed snap-ins; these might include, for example, DNS manager or device manager. Multiple copies of a particular snap-in can be added to apply to separate workstations. Snap-ins for MMC can include those from other vendors as well as Microsoft. Many companies, including IBM, Hewlett-Packard, NetIQ, Seagate, Symantec and Compuware, are also making MMC snap-ins; users can develop snap-ins to administer their own systems and custom applications.