ktor

Ktor is a web framework written in Kotlin, an official JetBrains project. Kotlin is a programming language widely used for Android development and server-side applications. A web framework is a set of tools and conventions that makes it faster to build applications that handle HTTP requests and responses, such as APIs and websites.

Ktor is designed around a few core ideas. It is asynchronous, meaning it can handle many requests at the same time without blocking threads. It achieves this using Kotlin coroutines, a language feature that makes it possible to write concurrent code that reads almost like sequential code. Avoiding thread blocking is important for server performance because blocking threads wastes memory and limits how many simultaneous users an application can serve.

The framework is intentionally unopinionated. It does not force you to use a particular database, logging library, template engine, or dependency injection system. Instead, it lets you install only the pieces you need through a plugin mechanism. This keeps small applications small and gives larger applications the flexibility to compose exactly the right stack.

Ktor applications are also straightforward to test. The framework includes a special test mode that simulates a web server without doing any real networking, so you can verify that your request routing and response logic work correctly without starting a live server.

Getting started involves adding Ktor as a dependency through Gradle or Maven (standard build tools for Kotlin and Java projects), writing a few lines of code to define routes and start the server, and running it with a single command. JetBrains provides an online project generator at start.ktor.io to scaffold a new project with chosen plugins. Full documentation lives at ktor.io.