No-brainer Dark Mode for Next.js

September 18, 20221481 min

TIL: @pacocoursey next-themes. I've been pretty happy using @tailwindCSS and letting the system render the right theme for the user, but if you do want to add UI controls. Give this no-brainer a shot, here's how I did mine.

Set the provider and attribute to display the active theme as a class. This will enable all dark classes present in the HTML tree. Don't forget to declare this in your @tailwindCSS config file: module.exports = { darkMode: 'class' }:

import { ThemeProvider } from "next-themes";
import type { AppProps } from "next/app";

function MyApp({ Component, pageProps }: AppProps) {
    return (
        <ThemeProvider attribute="class">
                <Component {...pageProps} />
        </ThemeProvider>
    );
}

To consume and toggle the UI, use their useTheme hook. To avoid hydration errors, return a loading state of your choice until fully mounted:

import { useState, useEffect } from "react";
import { useTheme } from "next-themes";

import { SunIcon, MoonIcon } from "@heroicons/react/outline";

export default function ThemeToggler() {
    const { resolvedTheme, setTheme } = useTheme();
    const [mounted, setMounted] = useState(false);

    useEffect(() => { setMounted(true) }, []);

    if (!mounted) return <></>;

    return (
        <button
            onClick={() => {
                setTheme(resolvedTheme === "dark" ? "light" : "dark");
            }}
        >
            {resolvedTheme === "dark" ? <SunIcon /> : <MoonIcon />}
        </button>
    );
}

It is that simple. It has 74,528 weekly npm downloads and if it's good enough for @leeerob, it's good for me too. Get creative with your loading state and toggle button (or not && KISS). Check out their next-themes GH repo for more info.