Ktorgen is a 100% compile-time code generator for creating HTTP clients using Ktor Client and interface annotations, inspired by Retrofit and Ktorfit.

🔹 No runtime dependencies — you only need the annotations and the compiler in your build.

🔹 100% compatible with Kotlin, Kotlin Multiplatform, KSP 2, and Ktor Client.

🔹 100% Ktor configuration — no unnecessary overhead or wrappers added.

🔹 Annotation retention: SOURCE, BINARY (only for RequiresOptIn).

🔹 Generated code annotated with @Generated and @Suppress to avoid warnings and exclude of analysis tools.

🔹 Support suspend fun, Coroutines Flow and Result out of the box.

🔹 Optional type-safe headers, using Headers.ContentTypes or Headers.Companion.*

🔹 Optional inheritance between interfaces (use delegation to implement).

🔹 Experimental support for vararg parameters and Pair type.

📚 See more in documentation page.

Install KSP plugin

Install Ktor Client Core and an Engine

• Version Catalog

[versions]
ktorgen = "<current-version>"

[libraries]
ktorgen-annotations = { group = "io.github.kingg22", name = "ktorgen-annotations", version.ref = "ktorgen" }
ktorgen-compiler = { group = "io.github.kingg22", name = "ktorgen-compiler", version.ref = "ktorgen" }

• Gradle for Kotlin JVM (KMP projects see below)

dependencies {
  implementation("io.github.kingg22:ktorgen-annotations:<current-version>")
  ksp("io.github.kingg22:ktorgen-compiler:<current-version>")
}

BREAKING CHANGES:

• Since PR #1, Header annotations have been different:

  Before this PR, the API of annotation is "identical" to Retrofit annotations.

  Before on functions @Headers("Content-Type: application/json") after @Header("Content-Type", "application/json")

  Before on parameters @Header("Content-Type") param: String after @HeaderParam("Content-Type") param: String

Migrating is as simple as:

Changing annotation imports to io.github.kingg22.ktorgen.http.*

Comma-separated header annotations are now repeatable and type-safe.

Before:

@Headers("Content-Type: application/json", "Accept: application/json")
suspend fun request(@Header("Authentication") token: String): String

After:

@Header("Content-Type", "application/json")
@Header("Accept", "application/json")
suspend fun request(@HeaderParam("Authentication") token: String): String

Passing your own Ktor HttpClient to the implementations, like this: fun UserRoute(client) for interface UserRoute and generated class _UserRouteImpl.

Real-life migration example: deezer-client-kt

• Add a matrix compatibility test on CI (Kotlin versions, KSP versions, Ktor Client versions) to know the range of compatibility.
• Improve support for the default behavior of KSP in KMP projects.
• Add better sample projects.
• Improve the internal state of the processor to avoid unnecessary state-sharing between rounds. Includes: logging, tracing, validation, deferred symbols, etc.
• Add more options to customize the generated code. Includes: generated annotations, custom KDoc, etc.
• Add more options to the behavior of the processor. Includes: fail-fast, no-processing, no-tracing, etc.
• Add performance benchmarks.
• Add test for Fragment annotation
• Add test for Cookie annotation
• Resolve knowable issues described in #27
• Resolve issues related to unresolved references, multi-round processing, unexpected errors. EDIT: Most unresolved symbols are caused by google/ksp#2668 and platform-specific issues caused by Optional expectation of some annotations.

See more in GitHub Page

Open to contributions 🚀 First usage needs to open in samples folder, the IDE will sync and compile automatically all.

This repository is a fork of Ktorfit and Retrofit annotations, with my own changes and additions. It is not affiliated with Ktor, JetBrains, Kotlin, Ktorfit, or Retrofit. Credits to their respective authors.

License: Apache 2.0, same as Retrofit and Ktorfit.