# ktlint — Anti-Bikeshedding Kotlin Linter with Built-In Formatter

> An anti-bikeshedding Kotlin linter and formatter that enforces the official Kotlin coding conventions with zero configuration required.

## Install

Save as a script file and run:

# ktlint — Anti-Bikeshedding Kotlin Linter with Built-In Formatter

## Quick Use
```bash
# Install via Homebrew
brew install ktlint

# Check code
ktlint "src/**/*.kt"

# Auto-format
ktlint -F "src/**/*.kt"
```

## Introduction
ktlint enforces the official Kotlin coding conventions and the Android Kotlin style guide with no configuration needed. It combines linting and formatting in a single tool, eliminating style debates in code review by applying a consistent, opinionated standard.

## What ktlint Does
- Lints Kotlin files against the official Kotlin coding conventions
- Auto-formats code with the `-F` flag to fix style violations in place
- Runs as a standalone CLI, Gradle task, or Maven plugin
- Supports `.editorconfig` for customizing indentation and line length
- Provides a reporter API for custom output formats

## Architecture Overview
ktlint uses the Kotlin compiler embeddable library to parse source files into a PSI tree. Rules are visitors that inspect and optionally modify PSI nodes. The rule engine runs in two phases: first a lint pass to collect violations, then an optional format pass to apply fixes. Rules are loaded from the built-in standard rule set or from custom rule JAR files on the classpath.

## Self-Hosting & Configuration
- Install via Homebrew, SDKMAN, snap, or download the JAR from GitHub releases
- Use `.editorconfig` to set `indent_size`, `max_line_length`, and other formatting options
- Integrate with Gradle via the `ktlint-gradle` plugin or the official Gradle task
- Add a pre-commit hook with `ktlint installGitPreCommitHook`
- Disable specific rules with `ktlint_disabled_rules` in `.editorconfig`

## Key Features
- Zero-configuration default based on the official Kotlin coding conventions
- Built-in formatter that fixes violations rather than just reporting them
- EditorConfig support for project-specific overrides without a custom config file
- Git pre-commit and pre-push hook installation with a single command
- Custom rule set support via JAR files for organization-specific conventions

## Comparison with Similar Tools
- **Detekt** — covers broader analysis including complexity and code smells; ktlint focuses on formatting and style
- **IntelliJ formatter** — IDE-specific; ktlint runs in CI without an IDE
- **Spotless** — a multi-language formatting tool that can delegate to ktlint as a backend
- **Diktat** — a stricter rule set built on top of ktlint's infrastructure

## FAQ
**Q: Does ktlint require any configuration to get started?**
A: No. ktlint works out of the box with the official Kotlin coding conventions. Use `.editorconfig` only if you need to override defaults.

**Q: Can I use ktlint with Android projects?**
A: Yes. ktlint supports the Android Kotlin style guide variant and integrates with Gradle-based Android projects.

**Q: How do I suppress a rule for a specific block of code?**
A: Use `@Suppress("ktlint:standard:rule-name")` annotation or `// ktlint-disable` comments.

**Q: Does ktlint support Kotlin script files?**
A: Yes. ktlint analyzes both `.kt` and `.kts` files including Gradle build scripts.

## Sources
- https://github.com/ktlint/ktlint
- https://ktlint.github.io/ktlint/

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Source: https://tokrepo.com/en/workflows/asset-6fb6265e
Author: Script Depot