Nesting

AI Content

The Concept of CSS Nesting

CSS nesting is a feature that allows developers to write styles in a hierarchical way, mimicking the structure of the HTML elements they are styling. Instead of defining flat CSS rules for each selector individually, nested CSS enables the grouping of styles in a way that reflects the parent-child relationships of HTML elements. This approach improves the readability and maintainability of stylesheets, especially as websites become more complex. In traditional CSS, rules are often written globally, and this can lead to redundancy, especially when applying the same styles to elements that share similar characteristics or are part of the same component. CSS nesting solves this by allowing developers to define child or descendant elements within their parent selectors, making the stylesheet more intuitive and easier to maintain.

The Origins of CSS Nesting

Before native CSS nesting, developers often relied on CSS preprocessors like Sass, LESS, and Stylus. These tools introduced the concept of nesting, which allowed CSS to be written in a hierarchical, indented format. The need for such a feature arose as web development became more modular and component-based, particularly with the advent of frameworks like React and Vue, which encourage component encapsulation. Sass, one of the earliest and most popular CSS preprocessors, included nesting as one of its key features, enabling developers to write cleaner and more organized styles. It became widely adopted due to its ability to handle complex styling in a more manageable way. LESS followed suit, incorporating similar features. These preprocessors helped set the stage for the eventual inclusion of nesting in the official CSS specification. As web development evolved, the CSS Working Group began to see the benefits of nesting and decided to incorporate this feature directly into the CSS specification. This shift allowed developers to use native CSS nesting without relying on external tools, making the feature more accessible to a broader audience.

The Use of the Ampersand (&) in Nesting Selectors

One of the key features introduced by CSS preprocessors was the use of the ampersand (&) symbol, which acts as a reference to the parent selector within nested rules. In the context of nested CSS, the ampersand helps reduce redundancy by allowing developers to reference the parent class or element in child or pseudo-class selectors. For example, the ampersand can be used to apply styles to a specific state of the parent element (such as :hover) or to modify the parent’s class name. This shorthand significantly simplifies the process of creating complex styles and improves the maintainability of large codebases. It is particularly useful for handling pseudo-classes, modifier classes, or any situation where the relationship between elements must be defined with specificity. The ampersand (&) serves as a placeholder for the parent selector, allowing it to be dynamically inserted into the child rules. For example, when nesting, the ampersand can expand into full class names or pseudo-classes without having to repeat the parent selector.

Browser Support for Native CSS Nesting

As of 2025, native CSS nesting is becoming widely supported across modern browsers, though the degree of support varies. Some browsers have implemented it fully, while others are still rolling it out behind feature flags or in experimental modes.

Current Browser Support

• Chrome: Native support for CSS nesting has been stable since Chrome version 112. This means developers using recent versions of Chrome can take advantage of native nesting without any special flags or configurations.
• Firefox: Firefox introduced support for CSS nesting behind a feature flag, and it is expected to become stable in version 115, which was anticipated to be released in 2023. This indicates that Firefox users will soon be able to use CSS nesting natively without needing to enable experimental features.
• Safari: Safari has supported native CSS nesting since version 16.4, making it available to users of Apple devices across macOS and iOS.
• Edge: Since Microsoft Edge is based on Chromium, it supports CSS nesting from version 112, aligning with Chrome’s stable release. This ensures Edge users can use the feature on par with Chrome users.

Mobile Browser Support

Since mobile browsers typically follow the update cycles of their desktop counterparts, mobile versions of Chrome, Safari, and Edge are expected to support CSS nesting as well. Firefox's mobile version, which is dependent on the desktop version’s features, will likely follow suit when support becomes stable in Firefox 115. It’s important to note that browser support for newer CSS features can often lag on mobile devices, so developers should verify compatibility if they are targeting specific mobile platforms or older versions of mobile browsers.

The preceding content was AI generated.
"Research and Document the concept of CSS nesting..." prompt. ChatGPT, GPT-4o-mini, OpenAI, 6 Apr. 2025.

My Content

All the states of the above link are being styled with nesting which is clearly shown with the different colors. Nesting is really not difficult to work with; it's basically shorthand for different selectors that utilize the same part of a selector, whether that's id, class, or element. The & stands for whatever selector it's housed inside. The cool part is that it's an exact replica of the text, so somewhere you could use it which may not have been obvious is in selector hierarchy. Hierarchical selectors share the first part of their names, which comes from the overall parent, and the second part is unique to the specific element. Because of these use cases, navigation and cards are two website features that come to mind for being styled with nesting.