ProgIDs

ProgIDs, or Programmatic Identifiers, are textual identifiers used in the Microsoft COM (Component Object Model) framework to identify and create software components. A ProgID provides a human-readable name for a COM class, allowing languages and environments such as scripts to instantiate objects without needing to know the underlying globally unique identifier (GUID or CLSID).

In practice, ProgIDs are registered in the Windows registry and are used to map a friendly name to the component’s CLSID. When a program calls a COM object by its ProgID, the system looks up the corresponding CLSID and then creates an instance of that class. This translation enables languages like VBScript, JavaScript in Windows Script Host, and other automation hosts to instantiate COM objects easily. A common example is "Excel.Application," a ProgID that creates an instance of Microsoft Excel.

ProgIDs support versioning and stability through versioned and version-independent forms. A developer can expose multiple versioned ProgIDs for a single component (for example, App.Object.1, App.Object.2) while offering a VersionIndependentProgID that points to the current version. This allows existing scripts to continue functioning when a newer version is installed, by updating the CurVer linkage to the desired versioned ProgID.

Related concepts include CLSID (the actual class identifier), AppID (used for security and activation), and the broader registry structure that stores COM metadata. ProgIDs play a key role in the interoperability of software components on Windows, balancing human readability with the capabilities of the COM activation process.