Plug

Plug is a specification and set of utilities for building composable modules in Elixir web applications. It defines a standard connection interface, allowing developers to create “plugs” that act as middleware for handling requests and responses. Examples include parsing parameters, managing sessions, logging, or authentication, all of which can be plugged into a pipeline. Plug serves as the foundation for the Phoenix framework, which builds on it to deliver a full-featured web stack. The library supports both synchronous and streaming responses, making it adaptable to various web scenarios. Its modularity and composability promote clean, reusable code while remaining lightweight enough for microservices and APIs outside of Phoenix.