Plugin

A plugin is a software component that extends the capabilities of a host application. It provides a narrowly defined service or feature and is designed to be loaded into the host at runtime rather than being embedded in the core program. Plugins usually interact with the host through a defined API or plugin interface, allowing them to access the host’s services while remaining decoupled from its internal implementation.

The host defines a plugin framework or container that discovers, loads, configures, and manages plugins. Plugins can run in-process or in separate processes and may be loaded dynamically when the application starts or when needed. They rely on the host to supply data, services, and user interfaces, while the plugin itself contributes new behavior such as tools, filters, or integrations. Compatibility and dependency management are common concerns, as plugins depend on host versions and other components.

Plugin ecosystems are widespread. Web browsers historically supported plugins to extend rendering or media capabilities, while modern browsers favor extensions that modify behavior. Content management systems, notably WordPress, use plugins to add features without changing core software. In multimedia software, VST or AU plugins add instruments and effects; in graphics software, plugins add filters and import/export formats.

Security and quality considerations are important in plugin design. Since plugins run within the host’s environment, they can affect stability and security; reputable sources, code signing, sandboxing, and permission controls help mitigate risk. Users should manage updates and compatibility when the host software changes.