Railpack

Railpack is an open source build pack created by Railway as the successor to Nixpacks. The source is available on GitHub. Coolify uses Railpack as one of the build packs.

Railpack checks your git repository and automatically detects your programming language, installs dependencies, and configures build and start commands — all with zero configuration. It then builds an optimized Docker image using BuildKit.

Railpack can deploy both fully static websites and non-static applications. Once your repository is set up, you can use Coolify to deploy your project with ease.

How to use Railpack?

On Coolify you can only use Railpack on git-based deployments.

The setup steps are the same as Nixpacks — follow the Nixpacks guide but select Railpack instead of Nixpacks in the build pack selector (Step 4).

Deploying Static Websites

The steps for deploying a fully static website with Railpack are the same as Nixpacks. Follow the Nixpacks static site guide — the only difference is that Railpack is selected as the build pack.

Deploying Non-Static Applications

The steps for deploying a non-static application with Railpack are the same as Nixpacks. Follow the Nixpacks non-static guide — the only difference is that Railpack is selected as the build pack.

Advanced Configuration

Environment Variables

You can customize Railpack's behavior using environment variables prefixed with RAILPACK_. Below are the available variables:

For more details, see the Railpack Environment Variables documentation.

To add or modify environment variables in Coolify, simply click on the Environment Variables tab, where you can manage them easily.

Configuration file

Railpack supports specifying build configurations in a railpack.json file. If this file is present in the root of your repository, it will be automatically used. For example:

{
  "$schema": "https://schema.railpack.com",
  "packages": {
    "node": "22"
  },
  "steps": {
    "install": {
      "commands": ["npm install"]
    },
    "build": {
      "commands": ["npm run build"]
    }
  },
  "deploy": {
    "startCommand": "node dist/index.js"
  }
}

Adding $schema to your railpack.json enables autocomplete and validation in your editor.

For more details, refer to the Railpack Configuration File documentation.

Railpack vs Nixpacks

Railpack is the successor to Nixpacks, built by the same team at Railway. Key differences include:

Both build packs support automatic language detection, static site deployment, custom install/build/start commands, and environment variable configuration.