CSS Nesting Documentation

What is CSS Nesting?

CSS nesting is a feature that allows selectors to be placed inside other selectors, mimicking the structure of HTML and improving code readability. This makes it easier to maintain large stylesheets and write hierarchical styles in a cleaner way.

Origins of CSS Nesting

CSS nesting was originally made popular through preprocessors like Sass and Less, which allowed developers to nest selectors and create modular, component-based styles. With increasing demand for native support, the CSS Working Group began formalizing nesting into the official CSS spec. Today, native CSS nesting is supported in major browsers without needing preprocessors.

Using the Ampersand (&) as a Nesting Selector

The ampersand & is used in CSS nesting to refer to the parent selector. This makes it possible to add pseudo-classes or create complex relationships without repeating the parent selector’s name. For example:

.button {
  color: white;
  background: blue;

  &:hover {
    background: navy;
  }

  &::after {
    content: " →";
  }
}

In this example, &:hover becomes .button:hover and &::after becomes .button::after.

Browser Support

As of April 2025, CSS nesting is supported in:

• Chrome 112+
• Edge 112+
• Safari 16.5+
• Firefox 117+

Older browsers may require polyfills or fallback styles.

Created by Me

I created a simple example using CSS nesting:

<button class="button">Click Me</button>

Summary: The button is styled with base styles and also uses the &:hover pseudo-class and &::after pseudo-element using the ampersand syntax to keep related rules grouped.

Why the information has value: CSS nesting allows developers to write DRY (Don’t Repeat Yourself) code, making it easier to follow the logical structure of the component-based layout.

How I would use it: I would use nesting in a real-world project to simplify component styles. It’s especially useful in larger UI systems where buttons, cards, forms, and nav elements share common structure and states (like hover or focus).

AI Contribution & Citation

This summary and description were created in collaboration with generative AI.

Formal Citation:
"Created Using Generative AI\nResearch and Document the concept of CSS nesting. Discuss the origins of CSS nesting. Discuss the use of the ampersand as nesting selector. Discuss browser support based on data from the caniuse.com website.\nCreated By You\nThen create an example of HTML and CSS using CSS nesting and the nesting selector ampersand.\nDescribe what on the demo page is being styled by the CSS nesting code.\nHow the ampersand was used as a nesting selector.\nHow you would use nesting in a project." prompt. ChatGPT, GPT-4, OpenAI, 09 Apr. 2025, https://chat.openai.com.