// THE ECOSYSTEM

One platform. Four ecosystems. 200+ modules.

Everything ships under a single platform version, so it just works together. Each sub-ecosystem has its own focus - but they all share the same functional soul, the same test-first ethos, and minimal dependencies. Pull in only what you need.

// FOUR FAMILIES

Same platform version. Different jobs.

Start in Core and reach into the others as you need them. Nothing is bundled you didn't ask for.

Apache 2.0

The foundation: server-as-a-function, routing, typesafe lenses, clients, formats and a testing toolkit. Zero dependencies, runs on any backend.

ServersClientsRoutingOpenAPITestingWebSockets
Explore http4k Core →
Apache 2.0

Lightweight adapters for LLM providers and AI services - with full Fake implementations so you can test AI integrations offline, deterministically and for free.

OpenAIMCPA2ALLM adaptersFakes
Explore http4k AI →
Apache 2.0

Typed, lightweight clients for popular cloud & SaaS APIs, each with a stateful in-memory Fake - so you can plug everything together and test without touching real infrastructure.

S3DynamoDBSQSRedisFakes
Explore http4k Connect →
Commercial

Commercially-licensed power tools for teams running http4k for real - free for individuals and small teams.

WiretapWebAuthnMCPX402Hot Reload
Explore http4k Pro →
Running http4k where it counts? http4k Enterprise bundles every Pro module with Long-Term Support and supply-chain security tooling - verified, signed, auditable artifacts for regulated teams.
// ONE VERSION TO RULE THEM

Install the platform once. Never align versions by hand again.

The http4k BOM pins every module across all four ecosystems to a single, tested platform version. Add the BOM, then declare the modules you want - no versions, no clashes.

  • Guaranteed-compatible across Core, AI, Connect & Pro
  • Add only the modules you actually use
  • Core has zero transitive dependencies
build.gradle.kts
dependencies {
    // the platform - one version
    implementation(platform("org.http4k:http4k-bom:6.54.0.0"))

    // ...then pick modules, no versions
    implementation("org.http4k:http4k-core")
    implementation("org.http4k:http4k-ai-openai")
    implementation("org.http4k:http4k-connect-amazon-s3")
}

Not sure where to start?

Most people begin in Core and reach into AI, Connect and Pro as they need them. Five minutes to your first running server.

Quickstart Browse the docs
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