CSS :root Selector

Last Updated : 09 Oct, 2024

The :root selector is a CSS pseudo-class that matches the root element of the document. In an HTML document, this is the <html> element.

While it behaves similarly to the html selector, the :root selector has higher specificity and is commonly used to define global styles or CSS custom properties (variables).

Syntax:

:root {
    /* CSS properties */
    background-color: lightgray;
    font-size: 16px;
}

The styles defined within the :root block will apply to the entire document unless overridden by more specific rules.

Basic Usage Examples

Example 1: Applying a Global Background Color

The following example sets the background color for the entire document using the :root selector:

html

<!DOCTYPE html>
<html>

<head>
    <title>root selector</title>
    <style>
        :root {
            background: green;
        }

        body {
            text-align: center;
        }

        h1 {
            color: white;
        }
    </style>
</head>

<body>
    <h1>GeeksforGeeks</h1>
    <h2>:root selector</h2>
    <p>The root of document is body tag</p>
</body>

</html>

Output:

Using the :root Selector for CSS Variables

The :root selector is particularly useful for defining CSS custom properties (variables), which can be used throughout the entire stylesheet for consistent theming.

Example: Defining and Using CSS Variables

HTML

<!DOCTYPE html>
<html>

<head>
      <title>Using CSS Variables with :root</title>
    <style>
       :root {
    --main-bg-color: #f0f0f0;
    --main-text-color: #333;
    --primary-color: #4CAF50;
    --font-size: 18px;
}

body {
    background-color: var(--main-bg-color);
    color: var(--main-text-color);
    font-size: var(--font-size);
}

button {
    background-color: var(--primary-color);
    color: white;
    padding: 10px 20px;
    border: none;
    cursor: pointer;
}

button:hover {
    background-color: darkgreen;
}
    </style>
</head>

<body>
    <h1>Themed Webpage Using :root</h1>
    <button>Click Me</button>
</body>

</html>