Tailwind CSS for Rails

Tailwind CSS is a utility-first CSS framework packed with classes like flex, pt-4, text-center and rotate-90 that can be composed to build any design, directly in your markup.

Installation

With Rails 7 you can generate a new application preconfigured with Tailwind by using --css tailwind. If you're adding Tailwind later, you need to:

1. Run ./bin/bundle add tailwindcss-rails
2. Run ./bin/rails tailwindcss:install

This gem wraps the standalone executable version of the Tailwind CSS v3 framework. These executables are platform specific, so there are actually separate underlying gems per platform, but the correct gem will automatically be picked for your platform.

Supported platforms are:

• arm64-darwin (macos-arm64)
• x64-mingw32 (windows-x64)
• x64-mingw-ucr (windows-x64)
• x86_64-darwin (macos-x64)
• x86_64-linux (linux-x64)
• aarch64-linux (linux-arm64)
• arm-linux (linux-armv7)

Using a local installation of tailwindcss

If you are not able to use the vendored standalone executables (for example, if you're on an unsupported platform), you can use a local installation of the tailwindcss executable by setting an environment variable named TAILWINDCSS_INSTALL_DIR to the directory containing the executable.

For example, if you've installed tailwindcss so that the executable is found at /node_modules/bin/tailwindcss, then you should set your environment variable like so:

TAILWINDCSS_INSTALL_DIR=/path/to/node_modules/bin

This also works with relative paths. If you've installed into your app's directory at ./node_modules/.bin/tailwindcss:

TAILWINDCSS_INSTALL_DIR=node_modules/.bin

Developing with Tailwindcss

Configuration

You can customize the Tailwind build through the config/tailwind.config.js file, just like you would if Tailwind was running in a traditional node installation. All the first-party plugins are supported.

The installer will create your Tailwind input file in app/assets/stylesheets/application.tailwind.css. This is where you import the plugins you want to use, and where you can setup your custom @apply rules. When you run rails tailwindcss:build, this input file will be used to generate the output in app/assets/builds/tailwind.css. That's the output CSS that you'll include in your app (the installer automatically configures this, alongside the Inter font as well).

Building for production

The tailwindcss:build is automatically attached to assets:precompile, so before the asset pipeline digests the files, the Tailwind output will be generated.

Building for testing

The tailwindcss:build task is automatically attached to the test:prepare Rake task. This task runs before test commands. If you run bin/rails test in your CI environment, your Tailwind output will be generated before tests run.

Update assets automatically

While you're developing your application, you want to run Tailwind in "watch" mode, so changes are automatically reflected in the generated CSS output. You can do this in a few different ways:

• use the Puma plugin to integrate "watch" with rails server, or
• run rails tailwindcss:watch as a separate process, or
• run bin/dev which uses Foreman

Puma plugin

The Puma plugin requires you to add this line to your puma.rb configuration:

plugin :tailwindcss if ENV.fetch("RAILS_ENV", "development") == "development"

and then running rails server will run the Tailwind watch process in the background

Run rails tailwindcss:watch

This is a flexible command, which can be run with a few different options.

If you are running rails tailwindcss:watch on a system that doesn't fully support file system events, pass a poll argument to the task to instruct tailwindcss to instead use polling: rails tailwindcss:watch[poll]. If you use bin/dev then you should modify your Procfile.dev.

If you are running rails tailwindcss:watch as a process in a Docker container, set tty: true in docker-compose.yml for the appropriate container to keep the watch process running.

If you are running rails tailwindcss:watch in a docker container without a tty, pass the always argument to the task to instruct tailwindcss to keep the watcher alive even when stdin is closed: rails tailwindcss:watch[always]. If you use bin/dev then you should modify your Procfile.dev.

Foreman

Running bin/dev invokes Foreman to start both the Tailwind watch process and the rails server in development mode based on your Procfile.dev file.

Debugging with unminified assets

If you want unminified assets, you can pass a debug argument to the rake task, i.e. rails tailwindcss:build[debug] or rails tailwindcss:watch[debug].

Note that you can combine task options, e.g. rails tailwindcss:watch[debug,poll].

Using with PostCSS

If you want to use PostCSS as a preprocessor, create a custom config/postcss.config.js and it will be loaded automatically.

For example, to enable nesting:

// config/postcss.config.js
module.exports = {
  plugins: {
    'postcss-import': {},
    'tailwindcss/nesting': {},
    tailwindcss: {},
    autoprefixer: {},
  },
}

Custom inputs or outputs

If you need to use a custom input or output file, you can run bundle exec tailwindcss to access the platform-specific executable, and give it your own build options.

Troubleshooting

Some common problems experienced by users ...

Conflict with sassc-rails

Tailwind uses modern CSS features that are not recognized by the sassc-rails extension that was included by default in the Gemfile for Rails 6. In order to avoid any errors like SassC::SyntaxError, you must remove that gem from your Gemfile.

Class names must be spelled out

For Tailwind to work, your class names need to be spelled out. If you need to make sure Tailwind generates class names that don't exist in your content files or that are programmatically composed, use the safelist option.

ERROR: Cannot find the tailwindcss executable for <supported platform>

Some users are reporting this error even when running on one of the supported native platforms:

• arm64-darwin
• x64-mingw32
• x64-mingw-ucrt
• x86_64-darwin
• x86_64-linux
• aarch64-linux

Check Bundler PLATFORMS

A possible cause of this is that Bundler has not been told to include native gems for your current platform. Please check your Gemfile.lock file to see whether your native platform is included in the PLATFORMS section. If necessary, run:

bundle lock --add-platform <platform-name>

and re-bundle.

Check BUNDLE_FORCE_RUBY_PLATFORM

Another common cause of this is that bundler is configured to always use the "ruby" platform via the BUNDLE_FORCE_RUBY_PLATFORM config parameter being set to true. Please remove this configuration:

bundle config unset force_ruby_platform
# or
bundle config set --local force_ruby_platform false

and re-bundle.

See https://bundler.io/man/bundle-config.1.html for more information.

"No such file or directory" running on Alpine (musl)

When running tailwindcss on an Alpine system, some users report a "No such file or directory" error message.

Install gnu libc compatibility

The cause of this is the upstream tailwindcss binary executables being built on a gnu libc system, making them incompatible with standard musl libc systems.

A fix for this has been proposed upstream at tailwindlabs/tailwindcss#6785, but in the meantime a workaround is to install compatibility libraries:

apk add build-base gcompat

Using asset-pipeline assets

In Rails, you want to use assets from the asset pipeline to get fingerprinting. However, Tailwind isn't aware of those assets. To use assets from the pipeline, use url(image.svg). Since Sprockets v3.3.0 url(image.svg) will then automatically be rewritten to /path/to/assets/image-7801e7538c6f1cc57aa75a5876ab0cac.svg. So the output CSS will have the correct path to those assets.

module.exports = {
    theme: {
        extend: {
            backgroundImage: {
                'image': "url('image.svg')"
            }
        }
    }
}

The inline version also works:

<section class="bg-[url('image.svg')]">Has the image as it's background</section>

Conflict with pre-existing asset pipeline stylesheets

If you get a warning Unrecognized at-rule or error parsing at-rule ‘@tailwind’. in the browser console after installation, you incorrectly double-process application.tailwind.css. This is a misconfiguration, even though the styles will be fully effective in many cases. The file application.tailwind.css is installed when running rails tailwindcss:install and is placed alongside the common application.css in app/assets/stylesheets. Because the application.css in a newly generated Rails app includes a require_tree . directive, the asset pipeline incorrectly processes application.tailwind.css, where it should be taken care of by tailwindcss. The asset pipeline ignores TailwindCSS's at-directives, and the browser can't process them.

To fix the warning, you can either remove the application.css, if you don't plan to use the asset pipeline for stylesheets, and instead rely on TailwindCSS completely for styles. This is what this installer assumes. Else, if you do want to keep using the asset pipeline in parallel, make sure to remove the require_tree . line from the application.css.

License

Tailwind for Rails is released under the MIT License. Tailwind CSS is released under the MIT License. The Inter font is released under the SIL Open Font License, Version 1.1.