React Native Android build fails — Gradle version or SDK mismatch

React Native Android build fails with Gradle errors, SDK version mismatches, or incompatible plugin versions. Common after updating React Native or adding a native module.

(1) Check RN upgrade helper for required Gradle changes: react-native-community.github.io/upgrade-helper. (2) SDK version mismatch: check android/build.gradle for compileSdkVersion, targetSdkVersion, minSdkVersion — native modules may require specific versions. (3) Gradle version: check android/gradle/wrapper/gradle-wrapper.properties. (4) Jetifier issues: npx react-native-clean-project or jetifier manually. (5) Duplicate class errors: check for transitive dependency conflicts in android/app/build.gradle, use exclude group. (6) Clear Gradle cache: cd android && ./gradlew clean && rm -rf ~/.gradle/caches. (7) NDK issues: ensure correct NDK version in local.properties.

Android's build system has many moving parts: Gradle version, AGP (Android Gradle Plugin) version, SDK versions, NDK, and Jetpack libraries must all be compatible. Native modules add their own version requirements.