actix-web/guide/src/qs_3.md

Application

Actix web provides some primitives to build web servers and applications with Rust. It provides routing, middlewares, pre-processing of requests, and post-processing of responses, websocket protcol handling, multipart streams, etc.

All actix web server is built around Application instance. It is used for registering handlers for routes and resources, middlewares. Also it stores applicationspecific state that is shared accross all handlers within same application.

Application acts as namespace for all routes, i.e all routes for specific application has same url path prefix:

   let app = Application::default("/prefix")
       .resource("/index.html", |r| r.handler(Method::GET, index)
       .finish()

In this example application with /prefix prefix and index.html resource get created. This resource is available as on /prefix/index.html url.