Kotlin Code Formatter & Beautifier

A Kotlin data class with nested when expressions, extension functions, coroutine builders, and DSL blocks — the concise syntax that makes Kotlin productive also makes it dense. Without consistent formatting, the scope boundaries blur and code becomes hard to navigate.

What Is a Kotlin Formatter?

A Kotlin formatter takes Kotlin source code and restructures it according to the official Kotlin coding conventions (the style enforced by ktlint and IntelliJ IDEA). It normalizes indentation, aligns when branches, formats lambda expressions, and ensures consistent spacing around operators and keywords. Whether you’re building Android apps, Kotlin Multiplatform projects, or backend services with Ktor, a formatter keeps the code clean and readable.

This tool supports:

• 4-space indentation — the Kotlin convention
• When-branch alignment — consistent formatting for when expressions
• Lambda formatting — trailing lambdas on the same line or properly indented
• DSL block indentation — proper nesting for Kotlin DSL builders

Kotlin Style Conventions

Kotlin’s official coding conventions are documented at kotlinlang.org and enforced by ktlint:

• 4 spaces for indentation — never tabs
• Opening brace on the same line as the declaration or control structure
• No semicolons — Kotlin doesn’t need them (and they’re discouraged)
• Trailing commas in multi-line parameter lists, constructor arguments, and when entries
• Single-expression functions use = syntax: fun double(x: Int) = x * 2
• Named arguments when calling functions with multiple parameters of the same type
• when over if-else chains when there are three or more branches

Common Use Cases

Android development: Format Kotlin code in Activities, Fragments, ViewModels, and Compose functions before code review. Consistent formatting is especially important in Compose’s declarative UI blocks.

Kotlin Multiplatform: When sharing code between Android, iOS, web, and desktop targets, consistent formatting across all platform-specific source sets maintains readability.

Coroutine code: Coroutine builders (launch, async, withContext) create nested scopes that are easy to misread without proper indentation.

DSL code: Kotlin DSLs (Gradle Kotlin DSL, Ktor routing, Compose UI) rely on nested lambda blocks. Proper formatting makes the DSL structure clear.

Frequently Asked Questions

Does this handle Jetpack Compose code? Yes. Compose functions, @Composable annotations, modifier chains, and nested composable blocks are formatted with proper indentation and spacing.

Can it format Kotlin DSLs? Yes. Kotlin DSL patterns — including Gradle Kotlin DSL (build.gradle.kts), Ktor routing, and custom DSL builders — are formatted as standard Kotlin code with proper lambda indentation.

Does it handle coroutine syntax? Yes. Coroutine builders (launch, async, runBlocking), suspend functions, flow builders, and structured concurrency patterns are formatted correctly.

Is my Kotlin code sent to a server? No. All formatting runs entirely in your browser. No code is transmitted to any server. Your source code stays completely private.