Installing the Compact Compiler

The Compact compiler transforms your Compact source code into ZK circuits that can run on the Midnight blockchain.

Understanding the Tools

Midnight provides two command-line tools:

In practice:

• Use compact compile for compilation: compact compile contract.compact output/
• Use compact update / compact check to manage toolchain versions, compact format to format code, and compact self check to update the devtools themselves (run compact --help for the full list — there is no scaffolding subcommand; new projects are created with npx create-mn-app)

⚠️ Important: The standalone compactc command is deprecated. Always use compact compile instead.

For the exercises in this book, we’ll use compact compile for compilation.

System Requirements

• Operating System: macOS or Linux (Windows via WSL2)
• Node.js: v22 or later
• Docker: For running the proof server

⚠️ Windows Users: You must use WSL2. PowerShell and Command Prompt are not supported.

Installation

Windows/WSL Only: you may need to install curl first:

sudo apt-get update && sudo apt-get install -y curl

Other OS: Install the Compact CLI using the official installer script:

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/midnightntwrk/compact/releases/latest/download/compact-installer.sh | sh

This downloads and installs the compact CLI, which includes the compactc compiler.

Update Your Shell PATH

The installer usually adds the binary to your PATH automatically. If not, add it manually:

export PATH="$HOME/.compact/bin:$PATH"

Then reload your shell:

source ~/.zshrc  # or source ~/.bashrc

Verifying Installation

After installation, verify that the tools are working:

compact --version

You should see output similar to:

compact 0.5.1

Test compilation works:

compact compile --help

Updating the Compiler

To update to the latest version:

compact update

Troubleshooting

Command not found

If you see “command not found”, add the Compact binary to your PATH:

export PATH="$HOME/.compact/bin:$PATH"

Add this line to your ~/.bashrc or ~/.zshrc to make it permanent.

Permission denied

If you encounter permission errors:

chmod +x ~/.compact/bin/compact

WSL-Specific Issues

For Windows users on WSL2, see the comprehensive troubleshooting guide in the Environment Setup chapter.

Next Steps

With the compiler installed, let’s set up the rest of your development environment.