Kotlin .gitignore Template Explained

Kotlin.gitignore is the Java template's rules plus the .kotlin/ directory used by the Kotlin Gradle plugin. Compiling Kotlin/JVM code produces the same .class and .jar files as Java.

It contains no build-tool rules. Most Kotlin projects use Gradle, so pick the Gradle template as well, or the Android template for Android apps.

Rules explained

Pattern	What it ignores and why
.kotlin/	Kotlin Gradle plugin dataStarting with Kotlin 2.0, the Gradle plugin stores data such as session information and error logs in a .kotlin folder at the project root. The Kotlin documentation also says to add this folder to .gitignore.
*.class*.jar*.war*.nar*.ear*.zip*.tar.gz*.rar	Compilation output and archivesJVM bytecode and distribution archives. They can be rebuilt from the source and build scripts alone.
hs_err_pid*replay_pid*	JVM crash logsDiagnostic files left when the JVM terminates abnormally.
*.log*.ctxt.mtj.tmp/	OtherRun logs and BlueJ/J2ME tool files. These rules are inherited unchanged from the Java template.

Practical notes

• To keep *.jar from ignoring the Gradle wrapper jar, place the Gradle template after Kotlin so that !gradle-wrapper.jar is applied last.
• If you target iOS with Kotlin Multiplatform, you also need Xcode/Swift-related rules and the macOS template.
• Handle IntelliJ IDEA settings with the JetBrains template.

Original template

# Compiled class file*.class# Log file*.log# BlueJ files*.ctxt# Mobile Tools for Java (J2ME).mtj.tmp/# Package Files #*.jar*.war*.nar*.ear*.zip*.tar.gz*.rar# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xmlhs_err_pid*replay_pid*# Kotlin Gradle plugin data, see https://kotlinlang.org/docs/whatsnew20.html#new-directory-for-kotlin-data-in-gradle-projects.kotlin/

Often used together

More template explanations