Serving single-page applications

Ktor provides the ability to serve single-page applications, including React, Angular, or Vue.

Add dependencies

To serve a single-page application, you only need the ktor-server-core dependency. Any specific dependencies are not required.

Serve an application

To serve a single-page application, you need to define where you want the content to be served from: a local filesystem or the classpath. You need at least to specify a folder/resource package containing a single-page application.

Serve framework-specific applications

You can serve a build of your single-page application created using a specific framework, such as React, Angular, Vue, and so on. Suppose we have the react-app folder in a project root containing a React application. The application has the following structure and the index.html file as the main page:

react-app
├── index.html
├── ...
└── static
    └── ...

To serve this application, call singlePageApplication inside the routing block and pass the folder name to the react function:

import io.ktor.server.application.*
import io.ktor.server.http.content.*
import io.ktor.server.routing.*

fun Application.module() {
    routing {
        singlePageApplication {
            react("react-app")
        }
    }
}

Ktor looks up index.html automatically. To learn how to customize a default page, see Customize serving settings.

Customize serving settings

To demonstrate how to serve a single-page application from resources, let's suppose our application is placed inside the sample-web-app resource package, which has the following structure:

sample-web-app
├── main.html
├── ktor_logo.png
├── css
│   └──styles.css
└── js
    └── script.js

To serve this application, the following configuration is used:

import io.ktor.server.application.*
import io.ktor.server.http.content.*
import io.ktor.server.routing.*

fun Application.module() {
    routing {
        singlePageApplication {
            useResources = true
            filesPath = "sample-web-app"
            defaultPage = "main.html"
            ignoreFiles { it.endsWith(".txt") }
        }
    }
}

useResources: Enables serving an application from a resource package.
filesPath: Specifies the path under which an application is located.
defaultPage: Specifies main.html as a default resource to serve.
ignoreFiles: Ignores paths that contain .txt at the end.

You can find the full example here: single-page-application.

20 October 2025