The Absolute Beginner's Guide to CSS Nesting

Introduction

CSS nesting allows you to nest CSS selectors within other selectors. This can help keep your CSS neat and organized.

What is CSS nesting?

CSS nesting is a feature that allows you to nest CSS selectors within other CSS selectors to create a relationship between the nested selectors. For example, you can nest a class selector within an element selector:

nav {
  background: blue;

  .menu-item {
    color: white;
  }
}

The .menu-item selector is nested inside the nav selector. This means the styling for .menu-item will only apply to menu items that are inside the element.

Why use CSS nesting?

Nesting can help organize your CSS and make it easier to read. It allows you to group related styles together. Nesting also lets you be more concise – you don’t have to repeat parent selectors.

Browser support for CSS nesting

Native CSS nesting is supported in most modern browsers, including Chrome, Firefox, Safari, and Edge. However, IE11 and earlier do not support it. Preprocessors like Sass and LESS provide nesting capabilities and can compile to browser-compatible CSS.

CSS Selectors Refresher

Before diving into nesting syntax, let’s recap some CSS selector basics:

Type selectors – Target elements by element name, like h1, div, etc.

Class selectors – Target elements by class name, denoted with a . prefix, like .menu.

ID selectors – Target elements by ID, denoted with a # prefix, like #navbar.

Attribute selectors – Target elements by attribute, like [type=”text”].

Pseudo-class selectors – Target elements based on state, like :hover or :active.

Nesting Basics

Nesting selectors

To nest a selector, simply put it inside the declaration block of the parent selector:

main {
  /* main styles */

  .box {
    /* box styles */
  }
}

This nests the .box selector inside main. The .box styles will only apply to boxes inside .

The ampersand

You can use the ampersand (&) to reference the parent selector from within a nested ruleset.

For example:

main {

  .box {

    &:hover {
      /* styles for hovered .box inside main*/
    }

  }

}

Nesting pseudo-classes

You can nest pseudo-classes like :hover, :active, etc. This is useful for state-based styles:

button {
  /* button styles */

  &:hover {
    /* button hover styles */
  }

  &:active {
    /* button active styles */
  }
}

This nests the hover and active pseudo-classes inside button.

Common Nesting Patterns

Nested media queries

Media queries can be nested inside other selectors:

“`css
.container {
/* styles */

@media (max-width: 600px) {
/* styles for screens <= 600px */
}
}

### Nested states

Nesting state-based pseudo-classes (:hover, :focus, etc.) inside the base selector keeps the related styles together:

css
button {
/* button styles */

&:hover {
/* button hover styles */
}

&:focus {
/* button focus styles */
}
}

### Nested descendant selectors

You can nest descendant selectors (e.g. .menu .item) to style elements inside of other elements:

css
.menu {

.item {
/* styles for .items inside .menu */
}

.link {
/* styles for .links inside .menu */
}

}

### Nested child selectors 

For first-level children, you can use the > combinator:

css
ul {
/* ul styles */

li {
/* styles for li children */
}
}
“`

Best Practices

Limit depth of nesting – Try to avoid nesting selectors more than 3 levels deep, as overly nested CSS can get hard to read.
Use Sass/LESS nesting carefully – If using a CSS preprocessor like Sass or LESS, be careful with nesting everything just because you can. Nest thoughtfully.
Nest for succinctness, not just because you can – Only nest when it makes your code more concise by avoiding repetition. Don’t nest just for the sake of nesting.

Conclusion

Nesting your CSS selects helps keep related styles together. It takes some practice to use effectively, but can make your CSS more organized, readable and reusable. Start simple and work your way up to more complex nesting as you get comfortable with the syntax.

The Absolute Beginner’s Guide to CSS Nesting