# Duplicate class found in modules

> Getting the error “Duplicate class found in modules”? Here is how to fix it. Two Android libraries ship the same class, usually Kotlin pulled in twice.

**Duplicate class found in modules.** Two dependencies include the same Java or Kotlin classes — usually different Kotlin standard library versions pulled in by plugins.

- Android build. Two libraries ship the same classes.
- Interactive page: https://capwr.app/free-tools/build-error-explainer/duplicate-class-found-in-modules
- Build error explainer: https://capwr.app/free-tools/build-error-explainer
- Last updated: 2026-10-03

## What this error means

Two dependencies include the same Java or Kotlin classes — usually different Kotlin standard library versions pulled in by plugins.

## Why it happens

Two dependencies on the release classpath ship the same classes. Plugin versions that pull different Kotlin standard-library artifacts are the common case.

## The message tools print

```
Duplicate class kotlin.collections.jdk8.CollectionsJDK8Kt found in modules kotlin-stdlib-1.8.22 (org.jetbrains.kotlin:kotlin-stdlib:1.8.22) and kotlin-stdlib-jdk8-1.7.10 (org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.7.10)
```

## How to fix it

1. Update the plugins involved so they agree on Kotlin.
2. Or align Kotlin by adding the Kotlin BOM (org.jetbrains.kotlin:kotlin-bom, with your Kotlin version) as a platform dependency in android/app/build.gradle.
3. Sync and build again.

## Check a log that shows this

Paste the failing step into the [build error explainer](https://capwr.app/free-tools/build-error-explainer). It matches this message, and any others in the same log, in your browser. Nothing is uploaded.

## Other Android build errors

- [Android SDK location not found](https://capwr.app/free-tools/build-error-explainer/android-sdk-location-not-found)
- [Android Gradle plugin requires Java 17 to run](https://capwr.app/free-tools/build-error-explainer/android-gradle-plugin-requires-java)
- [:capacitor-android project could not be found](https://capwr.app/free-tools/build-error-explainer/capacitor-android-project-could-not-be-found)
- [Android resource linking failed](https://capwr.app/free-tools/build-error-explainer/android-resource-linking-failed)
- [Keystore was tampered with, or password was incorrect](https://capwr.app/free-tools/build-error-explainer/keystore-was-tampered-with-or-password-incorrect)
- [Could not resolve all files for configuration](https://capwr.app/free-tools/build-error-explainer/could-not-resolve-gradle-configuration)

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