Setting Up Tailwind CSS in a New Rails 8 App

Recently, I needed to get Tailwind CSS running on a new Rails 8 app. Here’s how I got everything set up!

1. Create Your Rails App

Start by creating a new Rails app using the rails new command:

rails new tailwindcss_demo

Rails provides a shortcut by allowing you to pass the --css=tailwind option to rails new, which automatically sets up Tailwind. However, in my case, I already had a working Rails app and needed to add Tailwind manually. That’s what I’ll focus on here.

2. Install the Required Gems

The tailwindcss-rails gem provides all the necessary tooling to integrate Tailwind into a Rails app. Add it to your Gemfile and run bundle install:

# Gemfile
gem "tailwindcss-rails"

bundle install

3. Run the Tailwind Install Task

Next, run the Tailwind install task to set up the necessary files:

bin/rails tailwindcss:install

This command generates several files, including:

Tailwind Stylesheet

In app/assets/stylesheets/application.tailwind.css, you'll find the main Tailwind CSS file where you can add your styles:

@tailwind base;
@tailwind components;
@tailwind utilities;

/*
@layer components {
  .btn-primary {
    @apply py-2 px-4 bg-blue-200;
  }
}
*/

Tailwind Configuration

The install script also generates a Tailwind configuration file at config/tailwind.config.js:

const defaultTheme = require('tailwindcss/defaultTheme');

module.exports = {
  content: [
    './public/*.html',
    './app/helpers/**/*.rb',
    './app/javascript/**/*.js',
    './app/views/**/*.{erb,haml,html,slim}'
  ],
  theme: {
    extend: {
      fontFamily: {
        sans: ['Inter var', ...defaultTheme.fontFamily.sans],
      },
    },
  },
  plugins: [
    // require('@tailwindcss/forms'),
    // require('@tailwindcss/typography'),
    // require('@tailwindcss/container-queries'),
  ]
};

4. Running Tailwind in Development

The installation process also sets up a tailwind:watch task. This process runs alongside your Rails server and automatically rebuilds your frontend assets when changes are detected.

To start your Rails app with Tailwind watching for changes, use:

foreman start

The Tailwind install script will have added this process to your Procfile, ensuring that both your Rails server and the tailwind:watch task run together.

Conclusion

Setting up Tailwind CSS in a Rails app is straightforward, thanks to the tailwindcss-rails gem. If you're creating a new app, you can simplify the process by using rails new myapp --css=tailwind, which takes care of everything out of the box. However, if you’re adding Tailwind to an existing app, the steps above will get you up and running quickly!