Addins

Add-ins are software components that extend the functionality of a host application. They are designed to be loaded by the host rather than run as standalone programs, and they can introduce new features, automate repetitive tasks, integrate external services, or customize the user interface. Add-ins rely on the host’s extension framework and interact with the host through defined APIs, allowing developers to augment the application's capabilities without altering its core code.

Implementation and scope vary by platform, but common characteristics include modular packaging, runtime loading, and integration with the host’s UI. Add-ins may run in a variety of forms, such as libraries, scripts, or packaged modules, and they can appear as new commands, menus, toolbars, or task panes. They often operate within the host’s security model, possibly executing in restricted environments and requesting permissions for sensitive operations.

Development and distribution typically occur through a formal ecosystem. Hosts provide documentation, SDKs, and marketplaces or catalogs where developers publish add-ins. Users install add-ins from these sources, and updates can be delivered automatically by the host or the marketplace. Security considerations, such as code signing, restricted permissions, and isolation, are common concerns due to the heightened access add-ins may have within the host.

Examples span multiple domains. In productivity software, add-ins can add new analysis tools, automation features, or UI enhancements. In integrated development environments, they can supply language support, debuggers, or version control integration. In design and data software, add-ins extend rendering capabilities, data import/export options, or workflow automation. While related to plugins and extensions, add-ins are typically described in the context of extending a specific host application.