How to implement dark mode using TailwindCSS?

Kavin Desi Valli
·Mar 23, 2022·

8 min read

How to implement dark mode using TailwindCSS?

Photo by Lubo Minar on Unsplash

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Table of contents

  • Prerequisites
  • Setup
  • Setup html
  • Javascript
  • Tailwind dark variant.

Dark mode is something which has gained a lot of popularity in the last few years. Many popular websites are also implementing a dark mode on their website. However, dark mode can be a pain to setup if your css isn't well structured. Tailwind makes it very easy and instinctive to implement it. In this article, I'm going to go over how you can implement dark mode using Tailwind CSS.

Prerequisites

  • You should have a basic knowledge of Tailwind CSS.
  • You should know a little Javascript to understand how the theme toggle works.

Setup

Let's start by setting up a tailwind project. You also use bundlers like parcel, and this can also be used with any framework. Just setting up tailwind will be different and you can check that out here. I will be using it using npm without any bundler and with just HTML.

Create folder

mkdir dark-mode-tailwindcss
cd dark-mode-tailwindcss
npm init -y

You will see something like this Npm Init Output

Install Tailwind

npm i -D tailwindcss

Install Tailwind

Setup Tailwind

npx tailwindcss init

Initialize Tailwind Config

Open tailwind.config.js and make the following change:

-  content: [],
+  content: ['./**/*.html'],

This will look for all html files and look for tailwind classes through them. Now, let's create an html file to start off with

touch index.html

When to use Dark Mode?

Now, tailwind supports two ways of using Dark Mode. One is prefers-color-scheme and one is using classes. So, the way the former works is, if the users system's preferred mode is dark mode then it'll use dark mode else will use light mode. In the class based mode, it will be applied when the dark class is applied to any element before the current element in the tree. In this article, I'll be using classes just to demonstrate how to toggle between them, but feel free to use any. Not that prefers-color-scheme mode is used by default. To use class based mode you need to add the following line in tailwind.config.js

module.exports = {
+  darkMode: 'class',
   ...
}

Setup tailwind css file

Create a src directory with the tailwind css file

mkdir -p src/css
touch src/css/tailwind.css

and add the following contents to it

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

Setup css build commands

In your package.json make the following changes

...
  "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "css:build": "tailwindcss -i src/css/tailwind.css -o dist/css/tailwind.css",
+    "css:watch": "tailwindcss -i src/css/tailwind.css -o dist/css/tailwind.css --watch"
  },
...

And then run

npm run css:watch

Setup html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="./dist/css/tailwind.css" />
    <title>Tailwind Dark Mode</title>
  </head>
  <body>


  </body>
</html>

Now, this will be our starting point to the html. I've added the stylesheet which points to the compiled css generated by the Tailwind CLI.

I'm gonna setup a basic html site like so:

  <body>
    <div
      class="h-screen w-full bg-gray-100 dark:bg-gray-800 flex justify-center items-center"
    >
      <div class="bg-white text-gray-800 rounded-lg p-4 text-center">
        <h1 class="text-2xl font-bold">Tailwind Dark Mode</h1>
        <p>This is a demo of Tailwind CSS Dark Mode.</p>
      </div>
      <button
        class="absolute bottom-5 right-5 w-10 h-10 rounded-full bg-gray-800 flex justify-center items-center text-white"
        id="theme-toggle"
      >
        <svg
          width="24"
          height="24"
          viewBox="0 0 24 24"
          fill="none"
          xmlns="http://www.w3.org/2000/svg"
        >
          <path
            fill-rule="evenodd"
            clip-rule="evenodd"
            d="M12.2256 2.00253C9.59172 1.94346 6.93894 2.9189 4.92893 4.92891C1.02369 8.83415 1.02369 15.1658 4.92893 19.071C8.83418 22.9763 15.1658 22.9763 19.0711 19.071C21.0811 17.061 22.0565 14.4082 21.9975 11.7743C21.9796 10.9772 21.8669 10.1818 21.6595 9.40643C21.0933 9.9488 20.5078 10.4276 19.9163 10.8425C18.5649 11.7906 17.1826 12.4053 15.9301 12.6837C14.0241 13.1072 12.7156 12.7156 12 12C11.2844 11.2844 10.8928 9.97588 11.3163 8.0699C11.5947 6.81738 12.2094 5.43511 13.1575 4.08368C13.5724 3.49221 14.0512 2.90664 14.5935 2.34046C13.8182 2.13305 13.0228 2.02041 12.2256 2.00253ZM17.6569 17.6568C18.9081 16.4056 19.6582 14.8431 19.9072 13.2186C16.3611 15.2643 12.638 15.4664 10.5858 13.4142C8.53361 11.362 8.73568 7.63895 10.7814 4.09281C9.1569 4.34184 7.59434 5.09193 6.34315 6.34313C3.21895 9.46732 3.21895 14.5326 6.34315 17.6568C9.46734 20.781 14.5327 20.781 17.6569 17.6568Z"
            fill="currentColor"
          />
        </svg>
      </button>
    </div>

    <script src="./src/js/index.js"></script>
  </body>

Should show you something like this:

Starting HTML

I'm using the serve package by Vercel to serve my html. Just run npx serve from your project directory.

Javascript

We'll be needing a little bit of javascript to manage the dark mode. Add this in the index.html file:

...
+    <script src="./src/js/index.js"></script>
  </body>
...

Now, create an index.js file

mkdir src/js
touch src/js/index.js

Add the following to the index.js file.

const themeToggleButton = document.getElementById("theme-toggle");

const MOON_SVG = `<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M12.2256 2.00253C9.59172 1.94346 6.93894 2.9189 4.92893 4.92891C1.02369 8.83415 1.02369 15.1658 4.92893 19.071C8.83418 22.9763 15.1658 22.9763 19.0711 19.071C21.0811 17.061 22.0565 14.4082 21.9975 11.7743C21.9796 10.9772 21.8669 10.1818 21.6595 9.40643C21.0933 9.9488 20.5078 10.4276 19.9163 10.8425C18.5649 11.7906 17.1826 12.4053 15.9301 12.6837C14.0241 13.1072 12.7156 12.7156 12 12C11.2844 11.2844 10.8928 9.97588 11.3163 8.0699C11.5947 6.81738 12.2094 5.43511 13.1575 4.08368C13.5724 3.49221 14.0512 2.90664 14.5935 2.34046C13.8182 2.13305 13.0228 2.02041 12.2256 2.00253ZM17.6569 17.6568C18.9081 16.4056 19.6582 14.8431 19.9072 13.2186C16.3611 15.2643 12.638 15.4664 10.5858 13.4142C8.53361 11.362 8.73568 7.63895 10.7814 4.09281C9.1569 4.34184 7.59434 5.09193 6.34315 6.34313C3.21895 9.46732 3.21895 14.5326 6.34315 17.6568C9.46734 20.781 14.5327 20.781 17.6569 17.6568Z" fill="currentColor" /></svg>`;
const SUN_SVG = `<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M12 16C14.2091 16 16 14.2091 16 12C16 9.79086 14.2091 8 12 8C9.79086 8 8 9.79086 8 12C8 14.2091 9.79086 16 12 16ZM12 18C15.3137 18 18 15.3137 18 12C18 8.68629 15.3137 6 12 6C8.68629 6 6 8.68629 6 12C6 15.3137 8.68629 18 12 18Z" fill="currentColor" /><path fill-rule="evenodd" clip-rule="evenodd" d="M11 0H13V4.06189C12.6724 4.02104 12.3387 4 12 4C11.6613 4 11.3276 4.02104 11 4.06189V0ZM7.0943 5.68018L4.22173 2.80761L2.80752 4.22183L5.6801 7.09441C6.09071 6.56618 6.56608 6.0908 7.0943 5.68018ZM4.06189 11H0V13H4.06189C4.02104 12.6724 4 12.3387 4 12C4 11.6613 4.02104 11.3276 4.06189 11ZM5.6801 16.9056L2.80751 19.7782L4.22173 21.1924L7.0943 18.3198C6.56608 17.9092 6.09071 17.4338 5.6801 16.9056ZM11 19.9381V24H13V19.9381C12.6724 19.979 12.3387 20 12 20C11.6613 20 11.3276 19.979 11 19.9381ZM16.9056 18.3199L19.7781 21.1924L21.1923 19.7782L18.3198 16.9057C17.9092 17.4339 17.4338 17.9093 16.9056 18.3199ZM19.9381 13H24V11H19.9381C19.979 11.3276 20 11.6613 20 12C20 12.3387 19.979 12.6724 19.9381 13ZM18.3198 7.0943L21.1923 4.22183L19.7781 2.80762L16.9056 5.6801C17.4338 6.09071 17.9092 6.56608 18.3198 7.0943Z" fill="currentColor" /></svg>`;

let theme = localStorage.getItem("T_SITE_THEME") || "light";
theme === "light" ? setLightTheme() : setDarkTheme();

function setDarkTheme() {
  document.body.classList.add("dark");
  themeToggleButton.innerHTML = SUN_SVG;
  localStorage.setItem("T_SITE_THEME", "dark");
  theme = "dark";
}

function setLightTheme() {
  document.body.classList.remove("dark");
  themeToggleButton.innerHTML = MOON_SVG;
  localStorage.setItem("T_SITE_THEME", "light");
  theme = "light";
}

themeToggleButton.addEventListener("click", () => {
  if (theme === "light") {
    setDarkTheme();
  } else {
    setLightTheme();
  }
});

Ok, so let's go over this file and what it is doing.

  1. On line 1 - We're querying the toggle theme button from the dom
  2. On line 3 and 4 - We're setting two constants which correspond to a Moon SVG and a Sun SVG. This will be shown inside the toggle button.
  3. On line 5 - I'm setting a theme variable. Now, I'm querying from the localStorage the site's theme. If it exists, that means the user has already visited the website before and they have some preference. If not, set it to light by default. You can use dark if you want.
  4. On line 6 - Based on the theme, i'm either setting dark mode or light mode.
  5. In the setDarkTheme function - I'm first of all, adding the dark class to the body. This is essential for tailwind to understand that the user is using dark mode. Then, I'm changing the SVG inside the toggle button to that of a Sun. After that, we're resetting the value of our theme in the localStorage to dark and we're also resetting the value of the theme variable to dark.
  6. In the setLightTheme function - We're doing everything opposite to that in the setDarkTheme function.
  7. From lines 17 to 23 - We're handling the click event on the toggle theme button and setting dark mode or light mode accordingly.

Tailwind dark variant.

Now, how do we tell Tailwind to use which class in dark mode and which class in light mode? We do that using the dark variant which it provides us. For example, in the first div element on the page (just below the body tag), add this class:

-    <div class="h-screen w-full bg-gray-100 flex justify-center items-center">
+    <div class="h-screen w-full bg-gray-100 dark:bg-gray-800 flex justify-center items-center">

And checkout what happens when you refresh the site on the browser and click on the toggle theme button!

First view of dark mode

Notice the changes:

  1. The background color changes.
  2. If you inspect the body element, you will see a dark class on it.
  3. The localStorage T_SITE_THEME value changes to dark
  4. The svg inside the toggle theme button changes

Now, click on the button again:

Light Mode Again

Let's make a few changes in out html now:

-      <div class="bg-white text-gray-800 rounded-lg p-4 text-center">
+      <div class="bg-white dark:bg-gray-900 text-gray-800 dark:text-gray-200 rounded-lg p-4 text-center">
...
-      <button class="absolute bottom-5 right-5 w-10 h-10 rounded-full bg-gray-800 flex justify-center items-center text-white" id="theme-toggle">
+      <button class="absolute bottom-5 right-5 w-10 h-10 rounded-full bg-gray-800 dark:bg-gray-900 flex justify-center items-center text-white" id="theme-toggle">

Now your html should look like this:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="dist/css/tailwind.css" />
    <title>Tailwind Dark Mode</title>
  </head>
  <body>
    <div
      class="h-screen w-full bg-gray-100 dark:bg-gray-800 flex justify-center items-center"
    >
      <div
        class="bg-white dark:bg-gray-900 text-gray-800 dark:text-gray-200 rounded-lg p-4 text-center"
      >
        <h1 class="text-2xl font-bold">Tailwind Dark Mode</h1>
        <p>This is a demo of Tailwind CSS Dark Mode.</p>
      </div>
      <button
        class="absolute bottom-5 right-5 w-10 h-10 rounded-full bg-gray-800 dark:bg-gray-900 flex justify-center items-center text-white"
        id="theme-toggle"
      >
        <svg
          width="24"
          height="24"
          viewBox="0 0 24 24"
          fill="none"
          xmlns="http://www.w3.org/2000/svg"
        >
          <path
            fill-rule="evenodd"
            clip-rule="evenodd"
            d="M12.2256 2.00253C9.59172 1.94346 6.93894 2.9189 4.92893 4.92891C1.02369 8.83415 1.02369 15.1658 4.92893 19.071C8.83418 22.9763 15.1658 22.9763 19.0711 19.071C21.0811 17.061 22.0565 14.4082 21.9975 11.7743C21.9796 10.9772 21.8669 10.1818 21.6595 9.40643C21.0933 9.9488 20.5078 10.4276 19.9163 10.8425C18.5649 11.7906 17.1826 12.4053 15.9301 12.6837C14.0241 13.1072 12.7156 12.7156 12 12C11.2844 11.2844 10.8928 9.97588 11.3163 8.0699C11.5947 6.81738 12.2094 5.43511 13.1575 4.08368C13.5724 3.49221 14.0512 2.90664 14.5935 2.34046C13.8182 2.13305 13.0228 2.02041 12.2256 2.00253ZM17.6569 17.6568C18.9081 16.4056 19.6582 14.8431 19.9072 13.2186C16.3611 15.2643 12.638 15.4664 10.5858 13.4142C8.53361 11.362 8.73568 7.63895 10.7814 4.09281C9.1569 4.34184 7.59434 5.09193 6.34315 6.34313C3.21895 9.46732 3.21895 14.5326 6.34315 17.6568C9.46734 20.781 14.5327 20.781 17.6569 17.6568Z"
            fill="currentColor"
          />
        </svg>
      </button>
    </div>

    <script src="./src/js/index.js"></script>
  </body>
</html>

and the site like this:

Final Dark Mode The repository below has all the code used in this article

 
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