Implementing a Dark Mode Toggle in Laravel with Tailwind CSS 4

TailwindCSS 4 out the box supports prefers-color-scheme CSS media feature, I want class based dark mode support. To enable this add the following to your resources/css/app.css file

@custom-variant dark (&:where(.dark, .dark *));

This allows dark mode when the HTML tag has a class of dark.

Next create a toggle button. These has 2 icons for light mode and dark mode. Light is hidden by default. By adding a hidden class.

I’m using Heroicons that can be installed via blade-ui-kit/blade-heroicons

<button id="theme-toggle" class="p-2">
  <x-heroicon-o-sun id="theme-toggle-light" class="hidden size-5 text-yellow-500" />
  <x-heroicon-o-moon id="theme-toggle-dark" class="size-5 text-gray-900 dark:text-white" />
</button>

Next we need Javascript to handle click events when either icon is pressed.

Create a new file resources/js/dark.js reference it inside the resources/js/app.js file

import './dark';

Inside dark.js add:

document.addEventListener("DOMContentLoaded", applyTheme); // Fires on page load
document.addEventListener("livewire:navigated", applyTheme); // Fires for Livewire navigation
window.addEventListener("popstate", applyTheme); // Detects manual URL changes

function applyTheme() {
    const themeToggle = document.getElementById("theme-toggle");
    const themeToggleLight = document.getElementById("theme-toggle-light");
    const themeToggleDark = document.getElementById("theme-toggle-dark");

    function setTheme(mode) {
        if (mode === "dark") {
            document.documentElement.classList.add("dark");
            localStorage.setItem("theme", "dark");
            if (themeToggleLight && themeToggleDark) {
                themeToggleLight.classList.remove("hidden");
                themeToggleDark.classList.add("hidden");
            }
        } else {
            document.documentElement.classList.remove("dark");
            localStorage.setItem("theme", "light");
            if (themeToggleLight && themeToggleDark) {
                themeToggleDark.classList.remove("hidden");
                themeToggleLight.classList.add("hidden");
            }
        }
    }

    // Check saved theme or use system preference if no saved theme
    const savedTheme = localStorage.getItem("theme");
    if (savedTheme) {
        setTheme(savedTheme); // Apply the saved theme
    } else if (window.matchMedia("(prefers-color-scheme: dark)").matches) {
        setTheme("dark"); // Apply dark mode based on system preference
    } else {
        setTheme("light");
    }

    // Add event listener for the theme toggle button
    if (themeToggle && !themeToggle.dataset.listenerAdded) {
        themeToggle.addEventListener("click", () => {
            const isDark = document.documentElement.classList.contains("dark");
            setTheme(isDark ? "light" : "dark");
        });
        themeToggle.dataset.listenerAdded = true; // Prevent duplicate event listeners
    }
}

Now rebuilt your assets npm run build Now clicking on either icon should toggle the dark / light mode. Also the site will honor the visitors system preferences by default so if they are using dark mode, dark mode will load by default.