What is .kt?

.kt files contain source code written in the Kotlin programming language. Kotlin is a modern, statically typed language that runs on the Java Virtual Machine (JVM). It is fully interoperable with Java but offers a more concise syntax and modern features like null safety.

This quick guide explains when to use .kt files, how to open them on any device, and how to share them instantly with FileXhost.

When to use .kt files

You are building Android applications (it's Google's preferred language for Android).
You are developing server-side applications (Spring Boot supports Kotlin).
You want a language that is safer and more expressive than Java.
You are writing multiplatform code (Kotlin Multiplatform) for iOS and Android.

How to open .kt files

KT files are plain text and can be edited in any text editor. IntelliJ IDEA (by JetBrains, the creators of Kotlin) is the best IDE for Kotlin. Android Studio is the standard for Android development.

Algorithm details

Kotlin is a compiled language. The Kotlin compiler (kotlinc) translates .kt files into Java bytecodes (.class files) that can run on the JVM. It can also be compiled to JavaScript (Kotlin/JS) or native machine code (Kotlin/Native).

Browser & platform support

Direct: Not supported by browsers.
WebAssembly: Kotlin/Wasm allows compiling Kotlin code to WebAssembly for the browser.

Format comparison

Feature	Details
Conciseness	Drastically reduces boilerplate code compared to Java (e.g., data classes, type inference).
Safety	Built-in null safety eliminates the dreaded NullPointerException (The Billion Dollar Mistake).
Interoperability	You can use any existing Java library in Kotlin, and Java code can call Kotlin code.

How to create kt files

IntelliJ IDEA: File > New > Kotlin File.
Android Studio: Right-click > New > Kotlin Class/File.
CLI: 'touch main.kt'.

How to convert kt files

Compiler: 'kotlinc main.kt -include-runtime -d main.jar' creates a runnable JAR.
FileXhost: Upload to share source code.

Advantages & disadvantages

Advantages

Concise, expressive, and readable syntax
Null safety by default
Seamless interoperability with Java
Excellent tooling support (IntelliJ IDEA)

Disadvantages

Compilation speed can be slower than Java
Smaller community than Java (though growing rapidly)
Steep learning curve for developers new to functional programming concepts

Tools & software

IDEs

IntelliJ IDEA (Recommended), Android Studio, VS Code

Build Tools

Gradle, Maven

Compiler

kotlinc

Frequently asked questions

Is Kotlin better than Java?

Many developers consider it 'better' because it fixes many of Java's pain points (verbosity, nulls) while keeping the benefits of the JVM.

Can I use Kotlin for iOS?

Yes! Kotlin Multiplatform (KMP) allows you to share business logic between Android and iOS apps.

What is a .kts file?

It stands for 'Kotlin Script'. It's used for writing scripts (like Gradle build scripts) without defining a main function or class.

Technical specs

File type: Code
Extension: .kt
MIME type: text/x-kotlin, text/plain
Compression: Uncompressed
Max file size on FileXhost: Up to 25 MB per file on the free plan and up to 1 GB on Pro FileXhost accounts.

Upload your .kt file to FileXhost to get a clean, shareable URL in seconds. View the file in a modern browser, protect access with optional settings, and let others download it without any confusing ads or cluttered file pages.

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