Dark mode switch with pure CSS

May 24, 2021

Who knew it was possible to do a dark mode switch with pure CSS? I'll show you how to do mine, but feel free to adapt it as you want!

Dark mode switch with pure CSS

So here’s how to do a CSS-only dark mode for your website ! I’ll show you how to do mine, but feel free to adapt it as you want!

Why would I do that?

Writing JavaScript sucks
Consuming JavaScript as a client sucks
Accessibility: some people browse internet without internet, or with extensions like NoScript
It’s actually simple to do this with pure CSS, so why not?

How can CSS handle two possible states?

You probably wonder how can CSS change the color theme of a whole page. Because, knowing which color theme to display require a “switch”, something that can be “activated”… Is JavaScript the only solution?

No, these things exists in bare HTML too! There are many tags that are interactive. Here, we’ll use an input tag, with a checkbox. If the checkbox is checked, the Dark Mode will be active, and the Light Mode otherwise.

<input type="checkbox" id="dark-mode-switch" />

The CSS can access to the checkbox state with the :checked pseudo-class (there are many more!).

input#dark-mode-switch {
  /* Light Theme */
  background: #fff;
}

input#dark-mode-switch:checked {
  /* Dark Theme */
  background: #222220;
}

Changing the theme

There is a problem in the previous code snippet.

input#dark-mode-switch:checked {
  /* ↑ here */
  background: #222220;
}

We are selecting the switch itself, but it doesn’t matter to us, we want to change the whole body! And with CSS, it isn’t possible to select a parent tag…

But, it is possible to select a neighbour or a child tag, with CSS combinator! The A ~ B CSS combinator requires selector B to be an element with the same parent node as the selector A.

input#dark-mode-switch:checked ~ .general-theme {
  /* dark theme */
  background: #222220;
  color: #ddd;
}

.general-theme {
  /* light theme */
  background: #fff;
  color: #222;
}

Then, we’ll place the switch right after the body tag, and we’ll insert the whole site inside a div right after, just like this:

<head>
  <!-- your head --->
</head>
<body>
  <input type="checkbox" id="dark-mode-switch" />
  <div class="general-theme">
    <div class="my-website">
      <!-- your website content --->
    </div>
  </div>
</body>

Now, we need something to activate that checkbox: a label!

<label for="dark-mode-switch" class="ewen-toggle"> Toggle! </label>

You can place it wherever you want. But it’ll probably look ugly, so unless you know some CSS, if you want a fancy switch, just checkout the last chapter of this article for the code of this website’s switch ;)

Storing the theme

If you’ve gone this far and copy-pasted the code to your website, you might have noticed that when navigating, the theme isn’t stored. When the visitor goes from a Dark Mode activated page to another page, the theme goes back to Light Mode. How can we prevent that?

Unluckily, this isn’t just “displaying things” anymore. If you want your theme to be persistent across your pages, you have no other choice than using cookies or local storage, which require javascript.

var switcher = document.getElementById("dark-mode-switch");

// Click on dark mode icon. Store user preference through sessions
switcher.addEventListener("change", function () {
  // If dark mode is selected
  if (this.checked) {
    // set the a variable in user's browser
    localStorage.setItem("darkMode", "true");
  } else {
    // timeout of 100ms to avoid clipping
    setTimeout(function () {
      localStorage.setItem("darkMode", "false");
    }, 100);
  }
});

Now that the variable is set, we need to load user’s preference each time they visit the website. We’ll get the value from local storage, and simply check the checkbox we talked about earlier!

// Checks Storage. Keep user preference on page reload
if (localStorage.getItem("darkMode") === "true") {
  // Checking the checkbox
  switcher.checked = true;
}

I don’t consider it as a defeat: No-JS users that want dark mode will simply read your articles with Dark Mode activated, and navigate with light mode. Also, we’ve used CSS where it is possible and JS where it’s necessary, so everything is in the right place!

Setting defaults

It’s better to respect your visitor’s default settings for their first visit: it’s probably what they’ll want. You can set the default’s theme to their preferred color with the following code.

if (localStorage.getItem("darkMode") === null) {
  if (
    window.matchMedia &&
    window.matchMedia("(prefers-color-scheme: dark)").matches
  ) {
    // dark mode
    switcher.checked = true;
    localStorage.setItem("darkMode", "true");
  } else {
    switcher.checked = false;
    localStorage.setItem("darkMode", "false");
  }
}

And that’s it, enjoy! 😁

Appendix: a pretty switch

Just copy-paste this.

<div class="sidebar-toggler">
  <div class="ewen-toggle-wrapper">
    <label for="dark-mode-switch" class="ewen-toggle">
      <div class="ewen-toggle-track">
        <div class="ewen-toggle-track-moon">
          <img
            src="data:image/png;base64,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"
            role="presentation"
            style="pointer-events: none"
            width="16"
            height="16"
          />
        </div>
        <div class="ewen-toggle-track-sun">
          <img
            src="data:image/png;base64,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"
            role="presentation"
            style="pointer-events: none"
            width="16"
            height="16"
          />
        </div>
      </div>
      <div class="ewen-toggle-thumb"></div>
      <input
        class="ewen-toggle-screenreader-only"
        type="checkbox"
        aria-label="Switch between Dark and Light mode"
      />
    </label>
  </div>
</div>

.ewen-toggle {
  touch-action: pan-x;

  display: inline-block;
  position: relative;
  cursor: pointer;
  border: 0;
  padding: 0;

  -webkit-touch-callout: none;
  user-select: none;

  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
  -webkit-tap-highlight-color: transparent;
}

.ewen-toggle-screenreader-only {
  border: 0;
  clip: rect(0 0 0 0);
  height: 1px;
  margin: -1px;
  overflow: hidden;
  padding: 0;
  position: absolute;
  width: 1px;
}

.ewen-toggle-track {
  width: 50px;
  height: 24px;
  padding: 0;
  border-radius: 30px;
  background-color: #000;
}

#dark-mode-switch:checked ~ .general-theme .ewen-toggle-track {
  width: 50px;
  height: 24px;
  padding: 0;
  border-radius: 30px;
  background-color: #000;
}

.ewen-toggle-track-moon {
  position: absolute;
  width: 17px;
  height: 17px;
  left: 5px;
  top: 0px;
  bottom: 0px;
  margin-top: auto;
  margin-bottom: auto;
  line-height: 0;
  opacity: 0;
}

#dark-mode-switch:checked
  ~ .general-theme
  .ewen-toggle
  .ewen-toggle-track-moon {
  opacity: 1;
  background-color: #000 !important;
}

.ewen-toggle-track-sun {
  position: absolute;
  width: 17px;
  height: 17px;
  right: 5px;
  top: 0px;
  bottom: 0px;
  margin-top: auto;
  margin-bottom: auto;
  line-height: 0;
  opacity: 1;
  transition: opacity 0.25s ease;
}

#dark-mode-switch:checked ~ .general-theme .ewen-toggle-track-sun {
  opacity: 0;
}

.ewen-toggle-thumb {
  position: absolute;
  top: 1px;
  left: 1px;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background-color: #fafafa;
  box-sizing: border-box;
  transform: translateX(0);
}

#dark-mode-switch:checked ~ .general-theme .ewen-toggle-thumb {
  transform: translateX(26px);
  background-color: #fafafa;
}

.ewen-toggle-wrapper {
  justify-content: right;
  align-items: center;
}

The pretty button is forked from https://github.com/gaearon/overreacted.io, credits to Dan Abramov.