Migrating from KAPT to KSP: A Complete Guide to Kotlin's Future
Article Summary
Chamod Lakmal from PickMe reveals how switching annotation processors can cut Android build times in half. If you're still using KAPT, you're leaving serious performance gains on the table.
This comprehensive migration guide walks through replacing KAPT (Kotlin Annotation Processing Tool) with KSP (Kotlin Symbol Processing) for Android development. The article covers why KAPT's Java stub generation creates bottlenecks and provides step-by-step instructions for modernizing your build system.
Key Takeaways
- KSP delivers up to 2x faster compilation times compared to KAPT
- KAPT converts Kotlin to Java stubs first, adding overhead and losing type info
- Migration involves updating plugins, swapping kapt() for ksp() in dependencies
- Modern libraries prioritize KSP support over legacy KAPT
- Version catalogs approach shown for cleaner dependency management
Migrating from KAPT to KSP can improve build times by up to 50% while providing better Kotlin language support and lower memory consumption.
About This Article
Android developers using KAPT hit performance issues because the tool converts Kotlin to Java stubs during compilation. This creates memory overhead and slows down incremental builds, while also losing Kotlin-specific type information in the process.
You can replace KAPT with KSP by updating your build.gradle.kts file. Swap out the kapt() plugin and dependencies for ksp() equivalents, then update your generated code paths from build/generated/source/kapt to build/generated/ksp.
Teams that switch to KSP see build times improve by up to 50% and use less memory overall. You also get better support for Kotlin language features, and your project stays compatible with modern libraries that are moving away from KAPT.