Dark mode with Next.js and Tailwind

Adding dark mode to websites is increasingly common and thankfully this is quite easy to do nowadays. In this article I will explain how I usually go about adding dark mode when I can use Next.js and Tailwind. However, does not only work with Tailwind as the end result will just add the '.dark' or '.light' class to the html tag.

I'll skip over the basics of setting up Next.js and Tailwind as there are a ton of resources on that.

With tailwindcss you need to enable dark mode functionality in the config file.

/** @type {import('tailwindcss').Config} */
module.exports = {
  content: ['./src/**/*.{js,jsx}'],
  // enable dark mode based on classes
  darkMode: 'class',

If you have the tailwindcss extension installed you will notice that you can now style elements with a :dark modifier. In theory you could now write some code which adds the .dark and .light classes to the html element, but you have to get a few things right to avoid the wrong theme flashing on load with Next.js, saving the selected theme and defaulting to the users preferred theme. So instead of writing this code ourselves we can use a wonderful package called next-themes.

To get started with next-themes, simply install it using your package manager of choice. Then in _app.tsx you need to add a new provider, simply wrap any existing providers you might already have or just wrap the main component if this is the first global provider.

return (
  <ThemeProvider attribute="class" enableSystem>
    <Component {...pageProps} />

Note that we set the attribute to be class and enableSystem which defaults to the system setting for dark mode initially.

All that is left to do is to use the hook exposed by next-themes to get/set the current theme.

I'll add a theme selector implementation I did recently with tailwindcss, radix and next-themes to give you an idea on how to use it.

How to use the Radix Select as a dark mode selector

import {
} from '@heroicons/react/20/solid'
import * as SelectPrimitive from '@radix-ui/react-select'
import clsx from 'clsx'
import { AnimatePresence, motion } from 'framer-motion'
import { useTheme } from 'next-themes'
import { ComponentProps, useEffect, useState } from 'react'
import { IconButton } from './icon-button'

const themes = [
  { name: 'Light', value: 'light', icon: SunIcon },
  { name: 'Dark', value: 'dark', icon: MoonIcon },
  { name: 'System', value: 'system', icon: ComputerDesktopIcon },

export function ThemeSelector({ className }: { className?: string }) {
  const { resolvedTheme, theme, setTheme } = useTheme()

  // only use this component on the client, otherwise the selected theme will flash between values
  // could also use next/dynamic with ssr: false
  const [mounted, setMounted] = useState(false)
  useEffect(() => {
  }, [])
  if (!mounted) {
    return null

  return (
        onValueChange={(value) => {
        <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }}>
          <SelectPrimitive.Trigger asChild>
              <SelectPrimitive.Value className="text-gray-12" asChild>
                {resolvedTheme === 'light' ? <MoonIcon /> : <SunIcon />}

              'border-gray-6 max-w-xs overflow-hidden rounded-lg border shadow-lg',
              initial={{ opacity: 0 }}
              animate={{ opacity: 1 }}
              exit={{ opacity: 0 }}
              transition={{ duration: 0.2 }}
              <SelectPrimitive.ScrollUpButton className="text-gray-10 flex items-center justify-center">
                <ChevronUpIcon className="h-5 w-5" />

              <SelectPrimitive.Viewport className="bg-gray-3 rounded-lg p-2 shadow-lg">
                {themes.map((option) => (
                    className="text-gray-11 data-[highlighted]:text-gray-12 data-[highlighted]:bg-gray-4 active:bg-gray-5 relative flex select-none items-center gap-2 rounded-md py-2 pr-8 pl-2 text-sm font-medium focus:outline-none"
                    <option.icon className="h-4 w-4" />
                    <SelectPrimitive.ItemIndicator className="absolute right-2 inline-flex items-center">
                      <CheckIcon className="text-gray-12 h-5 w-5" />

              <SelectPrimitive.ScrollDownButton className="text-gray-10 flex items-center justify-center">
                <ChevronDownIcon className="h-5 w-5" />

The difference between theme and resolvedTheme is when theme is 'system' then resolvedTheme will be the actual value, so either 'dark' or 'light'.

You might notice that this example does not use the default tailwindcss colors but rather the Radix UI Colors. I might go over on how to set that up in a separate blog post, but the nice thing is that you get 'automatic' dark mode, no need to style anything with the :dark modifier. For now I only have a short twitter thread, feel free to check that out.

Let me know what you think or whether this was helpful at all.

Cheers ✌️