NOTE: The master branch now hosts the code for v5.x.x. Please refer to 4-x-stable branch for 4.x documentation.
Table of Contents
- Ruby 2.4+
- Rails 5.2+
- Node.js 10.13.0+
- Yarn 1.x+
- webpack 4.x.x
- ES6 with babel
- Automatic code splitting using multiple entry points
- Stylesheets - Sass and CSS
- Images and fonts
- PostCSS - Auto-Prefixer
- Asset compression, source-maps, and minification
- CDN support
- React, Angular, Elm and Vue support out-of-the-box
- Rails view helpers
- Extensible and configurable
You can either add Webpacker during setup of a new Rails 5.1+ application
# Available Rails 5.1+ rails new myapp --webpack
Or add it to your
# Gemfile gem 'webpacker', '~> 5.x' # OR if you prefer to use master gem 'webpacker', git: 'https://github.com/rails/webpacker.git' yarn add https://github.com/rails/webpacker.git yarn add core-js regenerator-runtime
Finally, run the following to install Webpacker:
bundle bundle exec rails webpacker:install # OR (on rails version < 5.0) bundle exec rake webpacker:install
Optional: To fix "unmet peer dependency" warnings,
yarn.lock changes, such as when pulling down changes to your local environment in a team settings, be sure to keep your NPM packages up-to-date:
/packs/application.js, include this at the top of the file:
import 'core-js/stable' import 'regenerator-runtime/runtime'
If you have styles imported in your pack file, you can link them by using
If you want to link a static asset for
<link rel="prefetch"> or
<img /> tag, you
can use the
<link rel="prefetch" href="<%= asset_pack_path 'application.css' %>" /> <img src="<%= asset_pack_path 'images/logo.svg' %>" />
If you are using new webpack 4 split chunks API, then consider using
tags for a pack and all the dependent chunks.
Important: Pass all your pack names when using
helper otherwise you will get duplicated chunks on the page.
Note: In order for your styles or static assets files to be available in your view, you would need to link them in your "pack" or entry file.
Webpacker ships with two binstubs:
Both are thin wrappers around the standard
executables to ensure that the right configuration files and environmental variables
are loaded based on your environment.
In development, Webpacker compiles on demand rather than upfront by default. This happens when you refer to any of the pack assets using the Webpacker helper methods. This means that you don't have to run any separate processes. Compilation errors are logged to the standard Rails log.
ruby ./bin/webpack-dev-server. Windows users will need to run these commands
in a terminal separate from
bundle exec rails s. This process will watch for changes
# webpack dev server ./bin/webpack-dev-server # watcher ./bin/webpack --watch --colors --progress # standalone build ./bin/webpack
Once you start this development server, Webpacker will automatically start proxying all webpack asset requests to this server. When you stop the server, it'll revert back to on-demand compilation.
You can use environment variables as options supported by
webpack-dev-server in the
WEBPACKER_DEV_SERVER_<OPTION>. Please note that these environmental
variables will always take precedence over the ones already set in the
configuration file, and that the same environmental variables must
be available to the
rails server process.
WEBPACKER_DEV_SERVER_HOST=example.com WEBPACKER_DEV_SERVER_INLINE=true WEBPACKER_DEV_SERVER_HOT=false ./bin/webpack-dev-server
By default, the webpack dev server listens on
localhost in development for security purposes.
However, if you want your app to be available over local LAN IP or a VM instance like vagrant,
you can set the
host when running
Note: You need to allow webpack-dev-server host as an allowed origin for
connect-src if you are running your application in a restrict CSP environment (like Rails 5.2+). This can be done in Rails 5.2+ in the CSP initializer
config/initializers/content_security_policy.rb with a snippet like this:
Rails.application.config.content_security_policy do |policy| policy.connect_src :self, :https, 'http://localhost:3035', 'ws://localhost:3035' if Rails.env.development? end
Note: Don't forget to prefix
ruby when running these binstubs on Windows
See docs/webpack for modifying webpack configuration and loaders.
Custom Rails environments
Out of the box Webpacker ships with - development, test and production environments in
config/webpacker.yml however, in most production apps extra environments are needed as part of deployment workflow. Webpacker supports this out of the box from version 3.4.0+ onwards.
You can choose to define additional environment configurations in webpacker.yml,
staging: <<: *default # Production depends on precompilation of packs prior to booting for performance. compile: false # Cache manifest.json for performance cache_manifest: true # Compile staging packs to a separate directory public_output_path: packs-staging
or, Webpacker will use production environment as a fallback environment for loading configurations. Please note,
NODE_ENV can either be set to
This means you don't need to create additional environment files inside
config/webpacker/* and instead use webpacker.yml to load different configurations using
For example, the below command will compile assets in production mode but will use staging configurations from
config/webpacker.yml if available or use fallback production environment configuration:
RAILS_ENV=staging bundle exec rails assets:precompile
And, this will compile in development mode and load configuration for cucumber environment if defined in webpacker.yml or fallback to production configuration
RAILS_ENV=cucumber NODE_ENV=development bundle exec rails assets:precompile
Please note, binstubs compiles in development mode however rake tasks compiles in production mode.
# Compiles in development mode unless NODE_ENV is specified ./bin/webpack ./bin/webpack-dev-server # compiles in production mode by default unless NODE_ENV is specified bundle exec rails assets:precompile bundle exec rails webpacker:compile
bundle update webpacker rails webpacker:binstubs yarn upgrade @rails/webpacker --latest yarn upgrade webpack-dev-server --latest # Or to install the latest release (including pre-releases) yarn add @rails/webpacker@next
Webpacker ships with basic out-of-the-box integration. You can see a list of available commands/tasks by running
bundle exec rails webpacker.
Included install integrations:
See Integrations for further details.
app files and compiled webpack bundles will go in your Rails app.
All these options are configurable from
The configuration for what webpack is supposed to compile by default rests
on the convention that every file in
or whatever path you set for
source_entry_path in the
is turned into their own output files (or entry points, as webpack calls it). Therefore you don't want to put anything inside
packs directory that you do not want to be
an entry file. As a rule of thumb, put all files you want to link in your views inside
"packs" directory and keep everything else under
Suppose you want to change the source directory from
frontend and output to
assets/packs. This is how you would do it:
# config/webpacker.yml source_path: frontend source_entry_path: packs public_output_path: assets/packs # outputs to => public/assets/packs
Similarly you can also control and configure
webpack-dev-server settings from
# config/webpacker.yml development: dev_server: host: localhost port: 3035
If you have
hmr turned to true, then the
stylesheet_pack_tag will create the appropriate HTML tags.
If you are adding Webpacker to an existing app that has most of the assets inside
app/assets or inside an engine, and you want to share that
with webpack modules, you can use the
option available in
config/webpacker.yml. This lets you
add additional paths that webpack should lookup when resolving modules:
You can then import these items inside your modules like so:
// Note it's relative to parent directory i.e. app/assets import 'stylesheets/main' import 'images/rails.png'
Note: Please be careful when adding paths here otherwise it will make the compilation slow, consider adding specific paths instead of whole parent directory if you just need to reference one or two modules
Webpacker hooks up a new
webpacker:compile task to
assets:precompile, which gets run whenever you run
assets:precompile. If you are not using Sprockets,
webpacker:compile is automatically aliased to
assets:precompile. Similar to sprockets both rake tasks will compile packs in production mode but will use
RAILS_ENV to load configuration from
config/webpacker.yml (if available).
When compiling assets for production on a remote server, such as a continuous integration environment, it's recommended to use
yarn install --frozen-lockfile to install NPM packages on the remote host to ensure that the installed packages match the
- v3 to v4 Upgrade Guide
We encourage you to contribute to Webpacker! See CONTRIBUTING for guidelines about how to proceed.
Webpacker is released under the MIT License.