javalin/javalin

Health v2 · maintenance only

Adoption not part of the score

8340 stars · 647 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Javalin is a lightweight, simple web framework for Java and Kotlin built on top of Jetty, supporting REST APIs, WebSockets, static file serving, and OpenAPI. It offers a fluent API designed for interoperability between Java and Kotlin with very few concepts to learn.

Use cases

• build a REST API in Java or Kotlin
• create a lightweight microservice on the JVM
• serve an SPA backend with static files from one server
• add websocket endpoints to a JVM application
• generate OpenAPI documentation with Swagger UI for a Java API
• replace Spring Boot with a simpler web framework
• run a small HTTP server with virtual threads support

When to choose

• you want a minimal, easy-to-learn REST API framework on the JVM
• you need Java and Kotlin interoperability with one consistent API
• you want Jetty-level performance with full Jetty configurability including SSL and HTTP3
• you prefer a Sinatra/Koa-style micro framework over heavyweight MVC frameworks

When to avoid

• you need a full MVC framework with built-in ORM, dependency injection, and batteries included
• your team is heavily invested in Spring ecosystem conventions
• you need reactive/non-blocking programming as the primary model

Facets

framework · maturity active

web-framework http-server routing websocket middleware api-framework web-development backend apis microservices jvm cross-platform rest-api jetty openapi micro-framework sinatra-inspired servlet

Member repositories

For agents

markdown · JSON · MCP: product_card(name="javalin/javalin")