# moon — Rust-Powered Build System for Web Monorepos

> An open-source build system and monorepo management tool written in Rust, designed for JavaScript, TypeScript, and polyglot web project workflows.

## Install

Save as a script file and run:

# moon — Rust-Powered Build System for Web Monorepos

## Quick Use
```bash
# Install moon
curl -fsSL https://moonrepo.dev/install/moon.sh | bash
# Initialize in your monorepo
moon init
# Run a task
moon run app:build
# Run affected tasks only
moon ci
```

## Introduction
moon is a build system and monorepo management tool built in Rust by moonrepo. It brings fast, reproducible task execution to JavaScript, TypeScript, and polyglot web projects with features like dependency-aware task orchestration, remote caching, and automatic affected-project detection.

## What moon Does
- Orchestrates tasks across monorepo packages with dependency awareness
- Detects affected projects from Git changes for efficient CI runs
- Provides remote caching to skip redundant builds across machines
- Manages toolchain versions (Node.js, Bun, Deno, Go, Python, Rust) automatically
- Generates project graphs and dependency visualizations

## Architecture Overview
moon uses a Rust core for performance-critical operations: hashing, dependency resolution, and task scheduling. Projects are defined in `moon.yml` files, and tasks run through a DAG-based executor that respects inter-project dependencies. The toolchain manager downloads and pins exact runtime versions per project. Remote caching stores task outputs keyed by input hashes, shared via moonbase or custom backends.

## Self-Hosting & Configuration
- Install the moon binary via the official install script or npm
- Run `moon init` to scaffold configuration in your monorepo root
- Define projects in `.moon/workspace.yml` and tasks in per-project `moon.yml`
- Configure remote caching with moonbase or a custom S3-compatible backend
- Integrate `moon ci` into your CI pipeline for affected-only builds

## Key Features
- Rust-powered performance with sub-millisecond task hashing
- Automatic toolchain version management across the team
- Built-in affected-project detection from Git diff analysis
- Remote caching to eliminate redundant CI work
- First-class support for JavaScript, TypeScript, Bun, Deno, Go, Python, and Rust

## Comparison with Similar Tools
- **Turborepo** — JS-focused, simpler but less polyglot support
- **Nx** — feature-rich but heavier, Node.js-based runtime
- **Bazel** — extremely powerful but steep learning curve for web teams
- **Lerna** — monorepo publishing tool, not a build system
- **Pants** — Python-focused polyglot build system, less web-oriented

## FAQ
**Q: Does moon replace npm/pnpm/yarn?**
A: No. moon orchestrates tasks on top of your existing package manager. It manages when and in what order tasks run, not package installation.

**Q: How does affected detection work?**
A: moon computes a hash of each project's source files and dependencies from the Git diff. Only projects with changed inputs (or downstream dependents) run in CI.

**Q: Can I use moon for non-JavaScript projects?**
A: Yes. moon supports Go, Python, and Rust toolchains alongside JavaScript/TypeScript, making it suitable for polyglot monorepos.

**Q: How does remote caching work?**
A: Task outputs are stored in a remote cache keyed by input hash. When another developer or CI run encounters the same inputs, the cached output is restored instead of re-running the task.

## Sources
- https://github.com/moonrepo/moon
- https://moonrepo.dev

---
Source: https://tokrepo.com/en/workflows/asset-46f5d2e8
Author: Script Depot