Node.js

Railpack builds and deploys Node.js applications with support for various package managers and frameworks.

Detection

Your project will be detected as a Node.js application if a package.json file exists in the root directory.

Versions

The Node.js version is determined in the following order of priority:

1. Set via the RAILPACK_NODE_VERSION environment variable
2. Read from the engines.node field in package.json
3. Read from the .nvmrc file
4. Read from the .node-version file
5. Read from mise.toml or .tool-versions files
6. Defaults to 22

This version resolution logic is applied consistently across all scenarios where Node is needed, including when Bun is the primary package manager but Node is required for native module compilation.

We officially support actively maintained Node.js LTS versions. Older versions of Node.js will likely still work but are not officially supported.

Node.js GPG verification is disabled by default; see the GPG verification recommendation to enable it in your project.

Runtime Variables

These variables are available at runtime:

NODE_ENV=production
NPM_CONFIG_PRODUCTION=false
NPM_CONFIG_UPDATE_NOTIFIER=false
NPM_CONFIG_FUND=false
NPM_CONFIG_FETCH_RETRIES=5
YARN_PRODUCTION=false
CI=true

Configuration

Railpack builds your Node.js application based on your project structure. The build process:

• Installs dependencies using your preferred package manager (npm, yarn, pnpm, or bun)
• Executes the build script if defined in package.json
• Sets up the start command based on your project configuration

Railpack determines the start command in the following order:

1. The start script in package.json
2. The main field in package.json
3. An index.js or index.ts file in the root directory

Config Variables

Variable	Description	Example
RAILPACK_NODE_VERSION	Override the Node.js version	22
RAILPACK_NO_SPA	Disable SPA mode	true
RAILPACK_SPA_OUTPUT_DIR	Directory containing built static files	dist
RAILPACK_PRUNE_DEPS	Remove development dependencies	true
RAILPACK_NODE_NPM_INSTALL	Custom npm install command	npm ci
RAILPACK_NODE_PRUNE_CMD	Custom command to prune dependencies	npm prune --omit=dev --ignore-scripts
RAILPACK_NODE_INSTALL_PATTERNS	Custom patterns to install dependencies	prisma
RAILPACK_ANGULAR_PROJECT	Name of the Angular project to build	my-app
RAILPACK_NX_APP	Nx app to build and start (project name, package name, or path)	web or @org/web
RAILPACK_NODE_PLAYWRIGHT_INSTALL	Install Playwright browsers	1

Playwright

When Playwright is a production dependency, Railpack suggests setting RAILPACK_NODE_PLAYWRIGHT_INSTALL=1. Browser installation is opt-in because it increases image size and is not required by every application that includes Playwright.

When enabled, Railpack runs Playwright through the detected package manager to install its browser binaries and adds the required runtime system packages. Ensure Playwright is included in your production dependencies so its CLI is available during the build.

Package Managers

Railpack detects your package manager in the following order:

1. packageManager field: Reads the packageManager field from package.json (uses Corepack to install the specified version)
2. Lock files: Falls back to detecting based on lock files:
   • pnpm-lock.yaml for pnpm
   • bun.lockb or bun.lock for Bun
   • .yarnrc.yml or .yarnrc.yaml for Yarn Berry (2+)
   • yarn.lock for Yarn 1
3. engines field: As a fallback, checks the engines field in package.json for package manager versions:
   • engines.pnpm for pnpm version
   • engines.bun for Bun version
   • engines.yarn for Yarn version
   • Defaults to npm if no package manager is detected

When the packageManager field is present, Railpack will use Corepack to install the specified package manager version. When a package manager is detected via the engines field, the specified version constraint will be used.

Railpack supports building native modules and automatically configures node-gyp.

Monorepo Support

Railpack automatically supports monorepo (workspaces) configurations with all major package managers. No special configuration is required.

Supported Approaches:

• npm, bun, yarn: Uses the workspaces field in package.json
• pnpm: Uses pnpm-workspace.yaml configuration
• Nx: Detects nx.json and builds Next.js apps even when targets are inferred (no root build/start scripts)

See the examples folder in the repository for workspace examples across different package managers (e.g., node-pnpm-workspaces, node-npm-workspaces, node-yarn-workspaces, node-bun-workspaces, node-nx-next).

When building a monorepo, Railpack will:

• Detect workspace configurations automatically
• Install all workspace dependencies correctly
• Respect workspace dependency links between packages
• Cache workspace node_modules appropriately

If your monorepo requires building a specific workspace package, ensure your build and start scripts are defined in the root package.json, set RAILPACK_NX_APP for multi-app Nx workspaces, or use a config file to specify custom commands.

Nx

Stock Nx workspaces often rely on inferred tasks instead of package.json scripts. When Railpack detects Nx and the root has no build/start scripts:

• Build: nx build <project> (uses the package name, e.g. @org/web)
• Start (Next.js): cd apps/web && next start so runtime does not depend on the nx CLI

With a single Next.js app, selection is automatic. With multiple apps, set RAILPACK_NX_APP to the project name, package name, or package path (e.g. web, @org/web, or apps/web).

Install

Railpack will only include the necessary files to install dependencies in order to improve cache hit rates. This includes the package.json and relevant lock files, but there are also a few additional framework specific files that are included if they exist in your app. This behavior is disabled if a preinstall or postinstall script is detected in the package.json file.

You can include additional files or directories to include by setting the RAILPACK_NODE_INSTALL_PATTERNS environment variable. This should be a space separated list of patterns to include. Patterns will automatically be prefixed with **/ to match nested files and directories.

Static Sites

Railpack can serve a statically built Node project with zero config. You can disable this behavior by either:

• Setting the RAILPACK_NO_SPA=1 environment variable
• Setting a custom start command

These frameworks are supported:

• Vite: Detected if vite.config.js or vite.config.ts exists, or if the build script contains vite build
• Astro: Detected if astro.config.js exists and the output is not type "server"
• Next.js: Detected if next is in dependencies and next.config.js, next.config.mjs, or next.config.ts sets output: 'export' (or output: "export"). The default next start start script does not disable SPA mode.
• CRA: Detected if react-scripts is in dependencies and build script contains react-scripts build
• Angular: Detected if angular.json exists
• React Router: Detected if react-router.config.js or react-router.config.ts exists, or if the build script contains react-router build. To enable SPA mode, set ssr: false in your React Router config.
• Expo Web: Detected if expo and react-native-web are in dependencies and app.json sets expo.web.output to static or single

For all frameworks, Railpack will try to detect the output directory and will default to dist (or build/client/ for React Router, or out for Next.js static exports). Next.js reads distDir from your config when set. Set the RAILPACK_SPA_OUTPUT_DIR environment variable to specify a custom output directory. Railpack uses your app’s build script to produce the static output.

Note that if a SPA framework is not detected automatically, can you force SPA mode by specifying a RAILPACK_SPA_OUTPUT_DIR environment variable. This will enable SPA mode and serve the specified directory as a static site. Some of the SPA detection uses regexes on framework configuration files, which will fail if the default framework configuration files are customized.

Static sites are served using the Caddy web server and a default Caddyfile. You can overwrite this file with your own Caddyfile at the root of your project.

Node SPA deploys honor the index_fallback key in a Staticfile at the project root when set. SPA routing behavior is unchanged unless you set index_fallback: false (for example on multi-page Astro static sites) so unknown paths return 404 and serve 404.html when present.

Framework Support

Railpack detects and configures caches and commands for popular frameworks. Including:

• Next.js: Caches .next/cache for each Next.js app in the workspace
• Remix: Caches .cache
• Vite: Caches node_modules/.vite
• Tanstack Start: Caches node_modules/.vite
• Astro: Caches node_modules/.astro
• React Router: Caches .react-router
• Nuxt:
  • Start command defaults to node .output/server/index.mjs
  • Caches node_modules/.cache

As well as a default cache for node modules:

• Node modules: Caches node_modules/.cache (with the cache key node-modules)

Cache & Removing node_modules

When you add custom build commands that remove node_modules (such as npm ci), Railpack automatically detects this and removes the node_modules/.cache directory from the cache configuration for those steps. This prevents EBUSY: resource busy or locked errors that would otherwise occur when trying to remove a cached directory.

This automatic handling applies to build steps that contain commands like:

• npm ci
• rm -rf node_modules
• rimraf node_modules

The install step always retains its cache configuration regardless of the commands used.

System Dependencies

Railpack automatically installs system dependencies for Puppeteer:

• Puppeteer: When detected in workspace dependencies, Railpack installs all necessary system packages for running headless Chrome, including xvfb, chromium dependencies, and font libraries. Note that Puppeteer’s bundled Chromium does not support ARM64; if you need to run on ARM hardware, consider switching to Playwright or implementing a custom workaround (e.g. installing a system Chromium and pointing executablePath at it).