Skip to main content
Edit

Installation

This guide covers the standard Shakapacker install flow for Rails apps. For configuration details after installation, see the configuration guide.

Prerequisites​

Add the Gem​

New Rails App​

Rails v6+​

For a new Rails 6+ app, skip Rails' default JavaScript installer so Shakapacker can create the bundler files, then continue from the app root:

rails new myapp --skip-javascript
cd myapp
bundle add shakapacker --strict

Existing Rails App​

For an existing Rails app (5.2+), start from the app root and skip the rails new step.

bundle add shakapacker --strict

Run the Installer​

Run the Shakapacker installer from the Rails app root:

bundle exec rake shakapacker:install

The installer creates the default Shakapacker configuration, JavaScript entry point, bundler config, binstubs, and package dependencies for the selected bundler/transpiler setup.

Before running the installer, commit or stash local work. If generated files conflict with existing files, the default install prompts before overwriting. To choose non-interactive conflict handling, use one of these modes:

# Overwrite generated files without prompting
FORCE=true bundle exec rake shakapacker:install

# Keep existing files and create only missing generated files
SKIP=true bundle exec rake shakapacker:install

Accepted truthy values for FORCE and SKIP are true, 1, and yes case-insensitively. If both are set, FORCE wins.

Optional: Consolidate dev dependencies with a supplemental package (10.1+)​

The installer adds the managed-build stack to package.json as individual entries (shakapacker, webpack, webpack-cli, webpack-assets-manifest for webpack apps; shakapacker, @rspack/core, @rspack/cli, rspack-manifest-plugin for rspack apps). On Shakapacker 10.1+ you can optionally replace those four entries with a single shakapacker-webpack or shakapacker-rspack dependency. The supplemental package pulls in the same managed stack at the exact tested versions and has no runtime impact — adoption is opt-in. See the v10.1 supplemental packages migration guide for the before/after.

Package Manager Selection​

Shakapacker uses the package_json gem to update package.json and run the app's package manager. Selection is based on the packageManager field in package.json.

If packageManager is missing, shakapacker:install infers it from the lock file and the package manager version. Without a lock file, it defaults to npm unless PACKAGE_JSON_FALLBACK_MANAGER is set:

PACKAGE_JSON_FALLBACK_MANAGER=yarn bundle exec rake shakapacker:install
PACKAGE_JSON_FALLBACK_MANAGER=pnpm bundle exec rake shakapacker:install
PACKAGE_JSON_FALLBACK_MANAGER=bun bundle exec rake shakapacker:install

The packageManager field selects the package manager command. Shakapacker does not install the package manager or enforce that exact version. Use Corepack or your preferred toolchain setup to install npm, Yarn, pnpm, or Bun before running the installer.

If you use Yarn PnP, configure Babel with babel.config.js rather than a Babel config inside package.json. See customizing Babel config.

Choosing a Bundler or Transpiler​

New installs use webpack and SWC by default. To install with Rspack:

SHAKAPACKER_ASSETS_BUNDLER=rspack bundle exec rake shakapacker:install

To install with Babel instead of SWC:

JAVASCRIPT_TRANSPILER=babel bundle exec rake shakapacker:install

Most JavaScript packages are optional peer dependencies. The installer adds the subset needed for your selected bundler/transpiler setup.

See:

Verify the Install​

After installation, verify the generated config and build:

bundle exec rake shakapacker:verify_install
bin/shakapacker

For development with the dev server:

bin/shakapacker-dev-server

Then add the generated files to version control, including config/shakapacker.yml, config/webpack/ or config/rspack/, bin/shakapacker, bin/shakapacker-dev-server, and the app/javascript/packs/application.js entry point.

Next Steps​