Rails + Tailwind + @apply

TailwindCSS is an interesting concept. At it’s base layer, Tailwind provides a set of CSS classes which can be used as if it were inline CSS (style="color: hotpink;"). However, there is another, and in my opinion, more powerful way to use Tailwind.


Tailwind, by virtue of using PostCSS, adds access to @apply in your processed CSS. This allows you to use semantic names like class="nav" rather than class="bg-blue text-center shadow-md ...". To me, this is much more legible and much more maintainable.


Let us take a look at how we can use this in Rails. First, install and set up the tailwindcss-rails-webpacker package.

$ bin/bundle add tailwindcss-rails-webpacker
$ bin/rails tailwindcss:install
# Extra step as a demo, generate a page to test with.
$ bin/rails g controller root root

With this done, let’s write some CSS with Tailwind. Let’s pop open app/javascript/stylesheets/application.scss and add:

h1 {
  @apply p-2 mb-2 text-2xl text-center bg-blue-500 text-white shadow-md;
p {
  @apply text-center;

What is all this!? Those are the classes exposed by Tailwind:

Any element can be styled this way. Tags, classes, DOM ID, etc.


Many observers may point out that TailwindCSS is a substantial bundle. 274kb (2.8mb uncompressed). But what we just created is so little CSS, why would we load all of that? We shouldn’t. PostCSS and Webpacker will take care of compressing this for us. Let’s look at the production-mode file sizes:

$ RAILS_ENV=production bin/rails assets:precompile
$ RAILS_ENV=production RAILS_SERVE_STATIC_FILES=1 bin/rails s

Looking now, the CSS comes down to 1.52kb (3.93kb uncompressed). That size is much more manageable. PostCSS is going through our HTML/ERB and picking apart which CSS classes we’re using, and only including those in the bundle.


In conclusion, TailwindCSS is a new, popular, CSS framework which encourages custom CSS, but also encourages using standardizing things like padding and margin. This can be difficult to set up if you’re not managing your own pipeline, but Rails and the gems from above make setup trivial.