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How can I use CSS variables to create a dark mode toggle?

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How can I use CSS variables to create a dark mode toggle?

Asked on Apr 01, 2026

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CSS variables, also known as custom properties, allow you to define reusable values in your stylesheets, which makes implementing a dark mode toggle efficient and straightforward. Here's a basic example of how to achieve this.

<!-- BEGIN COPY / PASTE -->
    <style>
      :root {
        --bg-color: white;
        --text-color: black;
      }
      
      body {
        background-color: var(--bg-color);
        color: var(--text-color);
        transition: background-color 0.3s, color 0.3s;
      }
      
      .dark-mode {
        --bg-color: black;
        --text-color: white;
      }
    </style>
    
    <button onclick="toggleDarkMode()">Toggle Dark Mode</button>
    
    <script>
      function toggleDarkMode() {
        document.body.classList.toggle('dark-mode');
      }
    </script>
    <!-- END COPY / PASTE -->

Additional Comment:

CSS variables are defined using the syntax "--variable-name: value;" and can be accessed using "var(--variable-name)".
The ":root" selector targets the document's root element, making the variables globally accessible.
The "transition" property is used to animate the change in background and text colors smoothly.
The "toggleDarkMode" function adds or removes the "dark-mode" class, altering the CSS variables' values.

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How can I use CSS variables to create a dark mode toggle?

Asked on Apr 01, 2026

Answer

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