http4k/http4k

Health v2 · maintenance only

Flags: no_license

Adoption not part of the score

2783 stars · 281 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

http4k is a lightweight, functional HTTP toolkit for Kotlin where applications are just functions from Request to Response, with no annotations, reflection, or containers. It spans 200+ modules covering servers, clients, routing, testing, serverless, WebSockets, and integrations, all released under a single versioned BOM.

Use cases

• build http apis in kotlin without a heavy framework
• test http endpoints in-memory without starting a server
• write a kotlin http server as a simple function
• swap server backends like undertow or jetty with one line
• deploy kotlin http apps to serverless platforms like aws lambda
• consume http services with a uniform kotlin client
• tdd-driven development of http services
• test ai/llm integrations offline with fakes

When to choose

• you want a typesafe, testable, functional approach to HTTP in Kotlin
• you value minimal dependencies, immutability, and no reflection magic
• you need in-memory testing of HTTP apps in milliseconds
• you want one consistent model for serving and consuming HTTP

When to avoid

• you prefer annotation-driven or DI-container frameworks like Spring
• your team is not comfortable with functional programming style
• you need a non-JVM platform, since http4k targets the JVM/Kotlin ecosystem

Facets

framework · maturity stable

web-framework http-server http-client routing middleware testing websocket templating api-framework web-development backend apis developer-tools testing jvm serverless cloud kotlin functional-programming server-as-a-function tdd immutability no-reflection openapi serverless llm-adapters supply-chain-security docker

Member repositories

For agents

markdown · JSON · MCP: product_card(name="http4k/http4k")