Kotlinfirst

Kotlinfirst is a term used in software development to describe an approach that places Kotlin at the center of API design, libraries, and tooling. It refers to creating APIs and frameworks that are idiomatic in Kotlin, fully leveraging language features such as null-safety, coroutines, data classes, sealed classes, extension functions, and DSL capabilities, with Kotlin Multiplatform or JVM/JS/Native as primary targets. The term is not tied to an official Kotlin project but arises in discussions about improving Kotlin adoption and interoperability by prioritizing Kotlin-first design.

Origin and usage: The phrase began in community discussions in the late 2010s and 2020s as developers argued for Kotlin-native APIs rather than Java-native wrappers. It is used mainly by library authors and architects who want to reduce boilerplate and improve ergonomics for Kotlin developers.

Principles: The core principles include producing idiomatic Kotlin APIs, favoring Kotlin-native abstractions over Java equivalents, leveraging coroutines for asynchronous operations, providing Kotlin Multiplatform support, using Kotlin DSLs and type-safe builders, and maintaining comprehensive KDoc with stable Kotlin APIs.

Adoption and reception: Kotlinfirst is not an official standard and its adoption varies by project. Proponents claim it improves consistency and ergonomics, while critics caution against over-commitment to Kotlin-specific patterns that could hinder cross-language interoperability. Real-world examples cited include Ktor, Koin, and Exposed as exemplars of Kotlin-oriented design.