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swyx

Posted on • Updated on • Originally published at swyx.io

How to Set Up SvelteKit with Tailwind CSS

Jun 2021 update: This guide has been completely updated for SvelteKit@next.113 + Tailwind JIT! You can also see this guide

Aug 2021 update: try this first:

npm init svelte@next
npx svelte-add@latest tailwindcss
npm install

Prerequisites

I'm going to skip the preamble. You can read:

I will also assume you have SvelteKit set up:

npm init svelte@next my-app
cd my-app
npm install
npm run dev
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I strongly recommend picking at least the ESLint and Prettier options.

Step 1: Install deps

npm install -D svelte-preprocess tailwindcss autoprefixer postcss

# optional tailwind ui plugin
npm install @tailwindcss/ui
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Step 2: Setup Config Files

Add a tailwind.config.cjs file at the project root. (we use .cjs for now, or else the tailwind vs code extension complains it uses require when the rest of the project is in ESM).

// tailwind.config.cjs
module.exports = {
    mode: 'jit',
    // you dont need `purge: enabled: production` because you are using jit
    purge: [ 
      "./src/**/*.svelte",
      // may also want to include HTML files
      "./src/**/*.html"
    ],
    darkMode: 'class',
    theme: {
      extend: {},
    },
    variants: {},
    plugins: [],
  }
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Step 2A: Svelte Config with inline PostCSS

And now set it up inside of your Svelte bundler config as well:

// svelte.config.js
import preprocess from 'svelte-preprocess';
import tailwind from 'tailwindcss'
import autoprefixer from 'autoprefixer'

/** @type {import('@sveltejs/kit').Config} */
const config = {
    // Consult https://github.com/sveltejs/svelte-preprocess
    // for more information about preprocessors
    preprocess: preprocess({
        postcss: {
            plugins: [
                tailwind, 
                autoprefixer
            ]
        }
    }),

    kit: {
        // hydrate the <div id="svelte"> element in src/app.html
        target: '#svelte'
    }
};

export default config;
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Step 2B: Svelte Config with separate PostCSS for PostCSS nesting

ALTERNATIVELY you can also set up your postcss.config.js in a separate file (this seems to be better for the postcss nesting plugin to run).

We use PostCSS 7, not 8 (latest) for now, because... JavaScript. I've added in postcss-nesting because I like it - feel free to remove of course.

  • npm i -D postcss-load-config postcss@7 postcss-nesting@7
  • svelte.config.js:
    preprocess: preprocess({
        defaults: {
            style: 'postcss',
        },
        postcss: true,
    }),
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  • postcss.config.js

import tailwind from 'tailwindcss'
import autoprefixer from 'autoprefixer'
import nesting from 'postcss-nesting'

export default  {
    syntax: 'postcss-scss',
    plugins: [
        // Some plugins, like postcss-nested, need to run before Tailwind
        nesting(),
        tailwind(),

        // But others, like autoprefixer, need to run after

        autoprefixer(),
        // !dev &&
        //  cssnano({
        //      preset: 'default',
        //  }),
    ],
};
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However, this setup is still buggy when you actually try to nest CSS. I haven't figured it out yet and would like some help here if you are reading this.

Step 3: Add the Tailwind includes to your Svelte App

Create src/routes/__layout.svelte and add this:

<style global lang="postcss">
    @tailwind base;
    @tailwind components;
    @tailwind utilities;
</style>

<slot></slot>
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And that's it!

Optional: Dark Mode

I like using Dark mode with classes so you can let the user toggle it:

Put this in your app.html:

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <link rel="icon" href="/favicon.png" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link href="https://fonts.googleapis.com/css2?family=Varela+Round&display=swap" rel="stylesheet">
        <script>
            // On page load or when changing themes, best to add inline in `head` to avoid FOUC
            if (localStorage.theme === 'dark' || (!('theme' in localStorage) && window.matchMedia('(prefers-color-scheme: dark)').matches)) {
            document.documentElement.classList.add('dark')
            } else {
            document.documentElement.classList.remove('dark')
            }
        </script>
        %svelte.head%
    </head>
    <body class="dark:bg-gray-900 dark:text-gray-100">
        <div id="svelte">%svelte.body%</div>
    </body>
</html>
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What about Svelte classes!

Svelte has a class: binding syntax that didn't used to be supported by Tailwind. With Tailwind JIT, it has now been supported as of 2021!

What versions are you working with?!?

  "devDependencies": {
    "@sveltejs/adapter-netlify": "^1.0.0-next.17",
    "@sveltejs/kit": "^1.0.0-next.113",
    "@typescript-eslint/eslint-plugin": "^4.19.0",
    "@typescript-eslint/parser": "^4.19.0",
    "autoprefixer": "^9.8.6",
    "eslint": "^7.22.0",
    "eslint-config-prettier": "^8.1.0",
    "eslint-plugin-svelte3": "^3.2.0",
    "postcss": "^8.3.0",
    "postcss-load-config": "^3.0.1",
    "prettier": "~2.2.1",
    "prettier-plugin-svelte": "^2.2.0",
    "svelte": "^3.34.0",
    "svelte-check": "^2.0.0",
    "svelte-preprocess": "^4.7.3",
    "tailwindcss": "^2.1.4",
    "tslib": "^2.0.0",
    "typescript": "^4.0.0"
  },
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Reference Repos

More practical repos you can reference and run

You are supposed to be able to run npx svelte-add tailwindcss --jit - but as of time of writing it is very buggy and doesn't work.


Appendix: Prior content (Old outdated content)

Mar 2021 update: SvelteKit and Tailwind JIT were released this month and completely changed the game. Both are still in beta but strongly recommend checking out these templates and tools:

Jan 2021 update: minor update of config for Tailwind 2.0. I've also added alternative approaches at the bottom, scroll down

Sep 2020 update: Chris has shown a much easier way to do this than I originally outlined, so I have replaced my original notes with notes from his sample repo. There's a build speed tradeoff, I discuss alternatives at bottom.

On the latest Toolsday, Chris Dhanaraj said he had trouble finding documentation for adding Tailwind to Svelte.

Today I also needed to add Tailwind to a Svelte project, so I am writing this as a reference for myself. Setting up PostCSS with Svelte is something I have documented on the new Svelte Society site, but of course it could be better and more specifically tailored to Tailwind (which after all is "just" a PostCSS plugin).

So I am writing this for him and for me.

A quick aside on WHY Use Tailwind with Svelte, since Svelte offers scoped CSS by default: Tailwind offers a nicely constrained "design system" so you don't overuse Magic Numbers and it's easy to add responsive styling with Tailwind breakpoints. Because Tailwind has the developer experience of "inline styles", I also find it easier to delete and move HTML around without having to go back for the styling. I also like not having to name classes. I discuss more on Why Tailwind in general in a separate post.

I will assume you have a standard existing Svelte or Sapper project with no PostCSS/Tailwind set up. I'll also add in autoprefixer and postcss-nesting since I like to work with those, but of course feel free to remove as needed.

Note: this section used to involve messing with package.json scripts to run postcss-cli, but Chris realized that you didn't need to do any of this since Svelte already has a way to inject CSS and svelte-preprocess already runs on every Svelte file.

Please see:

To see this working in action.

Alternative Approaches

This method outlined above is simple to get running, but does end up running thousands of lines of Tailwind's CSS through the Svelte compiler. This may cause performance issues (primarily, every time you change the entry point file). Alternative approaches may be more appropriate depending on your preferences:

Discussion (29)

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dctalbot profile image
David Talbot

I followed these steps, but had major perf issues. Anyone else find the sveltePreprocess step to be very slow? Every change I made was taking around 18 seconds to reload the page. I sped it up by disabling source maps and purging, but it still took 11 seconds. I ended up rolling my own setup and now it takes 109ms. Still don't really understand what was going on, but I'm happy with my setup so I saved it here: github.com/dctalbot/svelte-typescr...
Cheers!

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khromov profile image
Stanislav Khromov

Hello and thank you for writing this tutorial!

I've followed along with it but ran into an issue - the resulting bundle.css does not have prefixed classes. It seems like PostCSS does not prefix them, unlike if you use a normal <style> tag where Svelte will prefix the classes.

I've added the prefix: 'my-prefix' setting to tailwind.config.js. It does work, but you have to write out the prefixed version in your code, so flex becomes my-prefix-flex, and so on. This gets old fast. 😅

In an ideal world, I would write the normal Tailwind classes and the resulting bundle would be automatically prefixed.

PS.
I've also tried the postcss-prefixer package, but then Svelte didn't include any of my classes in the bundle.css output. Perhaps i misconfigured it...

Thank you so much again and hope that you or someone else has solved this issue or have some suggestions for how to proceed!

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swyx profile image
swyx Author

no idea about that, sorry. I don't use any prefixes. perhaps check one of the alternative methods listed at the bottom to see if works

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sarioglu profile image
sarioglu

Here is another similar tutorial for Svelte and Sapper that I have written a while ago: dev.to/sarioglu/using-svelte-with-...

It also includes template repositories for both.

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swyx profile image
swyx Author

added, cheers. i think mine is a bit simpler tho

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mgrisole profile image
mgrisole

In my case I had to change the build script from:

"build": "rollup -c"
to
"build": "NODE_ENV=production rollup -c"

to actually purge unused css

Ref: tailwindcss.com/docs/optimizing-fo...

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dwstevens profile image
David Stevens

@swyx Have you seen WindiCSS? It seems to fix the overhead on the preprocess side. windicss.netlify.app/guide/svelte....

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malikbenkirane profile image
Malik Benkirane

Thank you! I'm going to try that right away

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malikbenkirane profile image
Malik Benkirane • Edited on

Although the project is very promising...
I have discovered some issues there with an {#each...} inside of an {#if...}
I have to dig into that but I don't get compiled class for this one and styles won't get applied.

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paul42 profile image
Paul.42

just curious, why the purge css ignore? don't you want purge CSS to remove unused styles from the base, or is purge css too aggressive?
Thanks for the article!

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swyx profile image
swyx Author

no reason - i'll be honest i blindly copied it from github.com/chrisdhanaraj/svelte-ta... but you're right, it's not needed, i took it out

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chrisdhanaraj profile image
Chris Dhanaraj

For context, I pulled that one from Tailwind's docs on Controlling File Size.

tailwindcss.com/docs/controlling-f...

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swyx profile image
swyx Author

dammit, lol nicely done. will add back with a note

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ercode profile image
Erkut TEKOĞLU

Thank you so much for this amazing guide!

I have gone with 2A option but my page not auto-reloading on tailwind css class changes.

Did I miss something?

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swyx profile image
swyx Author

no you did not... i had it broken as well but @abdelwahab313 helped me fix it. what version of sveltekit are you using? make sure it is the latest

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ercode profile image
Erkut TEKOĞLU

Everything has the latest version.
By the way, I found a quick solution for all just in 3 steps:

In the app directory,
(1) npm init svelte@next
(2) npx svelte-add@latest tailwindcss
(3) npm install

Everything is working great!
I would be very happy if you add this to the guide.

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swyx profile image
swyx Author

will do

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rraihansaputra profile image
raihan saputra

Hi Shawn, I'm trying out this config with the routify-ts template. I got the classes working, but seems like @apply directives doesn't work on my project. Did you get this working with this config?

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swyx profile image
swyx Author

it worked for me but I don't use Routify so I don't know how to help you

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rraihansaputra profile image
raihan saputra

Managed to get it working using your config. There was a duplicate preprocess key on my rollup config. Thank you for the write up!

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codechips profile image
Ilia Mikhailov

In case anyone needs to setup Sapper + Tailwind one day 🙂

sapper-with-postcss-and-tailwind.v...

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swyx profile image
swyx Author

added, cheers

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kevinast profile image
Kevin Bridges

Thanks for this reference @swyx . It proved to be invaluable for a new tailwind svelter!

BTW: You may want to mention that most likely you will want to remove the public/global.css reference (of the svelte template) so it does not interfere with tailwind css. This may be obvious to some, but I had several issues related to this.

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giorgosk profile image
Giorgos Kontopoulos 👀

Nice one @swyx perhaps you can add some tags #svelte #tailwind ?

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swyx profile image
swyx Author

oh word lol

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bwighthunter profile image
Blake Wight

Hmmm. Having issues with getting scss media queries working with this. Is there more I have to do to get that to work? Or should it just work?

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swyx profile image
swyx Author

oh no, i dont know, i dont use scss. it should just work.. if anything is wrong its probably your setup of svelte-preprocess

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jesuscovam profile image
jesuscovam • Edited on
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lalit64 profile image
Lalit Yalamanchili • Edited on

Can I suggest another method to add Tailwind to SvelteKit, I use it for all my projects.

jsco.dev/blog/how-to-set-up-tailwi...