@layer

The @layer CSS at-rule is used to declare a cascade layer and can also be used to define the order of precedence in case of multiple cascade layers.

Syntax

@layer layer-name {rules}
@layer layer-name;
@layer layer-name, layer-name, layer-name;
@layer {rules}

where:

layer-name

Is the name of the cascade layer.

rules

Is the set of CSS rules in the cascade layer.

Description

Rules within a cascade layer cascade together, giving more control over the cascade to web developers. Any styles not in a layer are gathered together and placed into a single anonymous layer that comes after all the declared layers, named and anonymous. This means that any styles declared outside of a layer will override styles declared in a layer, regardless of specificity.

The @layer at-rule is used to create a cascade layer in one of three ways.

The first way is to create a named cascade layer with the CSS rules for that layer inside, like so:

@layer utilities {
  .padding-sm {
    padding: 0.5rem;
  }

  .padding-lg {
    padding: 0.8rem;
  }
}

The second way is to create a named cascade layer without assigning any styles. This can be a single layer, as shown below:

@layer utilities;

Multiple layers can be defined at once, as shown below:

@layer theme, layout, utilities;

This is useful because the initial order in which layers are declared indicates which layer has precedence. As with declarations, the last layer to be listed will win if declarations are found in multiple layers. Therefore, with the preceding example, if a competing rule was found in theme and utilities, the one in utilities would win and be applied.

A rule in utilities would be applied even if it has lower specificity than the rule in theme. This is because once the layer order has been established, specificity and order of appearance are ignored. This enables the creation of simpler CSS selectors because you do not have to ensure that a selector will have high enough specificity to override competing rules; all you need to ensure is that it appears in a later layer.

Note: Having declared your layer names, thus setting their order, you can add CSS rules to the layer by re-declaring the name. The styles are then appended to the layer and the layer order will not be changed.

The third way is to create a cascade layer with no name. For example:

@layer {
  p {
    margin-block: 1rem;
  }
}

This creates an anonymous cascade layer. This layer functions in the same way as named layers; however, rules cannot be assigned to it later. The order of precedence for anonymous layers is the order in which layers are declared, named or not, and lower than the styles declared outside of a layer.

Another way to create a cascade layer is by using @import. In this case, the rules would be in the imported stylesheet. Remember that the @import at-rule must precede all other types of rules, except the @charset rules.

@import "theme.css" layer(utilities);

Nesting layers

Layers may be nested. For example:

@layer framework {
  @layer layout {
  }
}

To append rules to the layout layer inside framework, join the two names with a ..

@layer framework.layout {
  p {
    margin-block: 1rem;
  }
}

Formal syntax

@layer [ <layer-name># | <layer-name>?  {
  <stylesheet>
} ]

Examples

Simple example

In the following example, two CSS rules are created. One for the <p> element outside of any layer and one inside a layer named type for .box p.

Without layers, the selector .box p would have the highest specificity, and therefore, the text Hello, world! will display in green. As the type layer comes before the anonymous layer created to hold non-layer content, the text will be purple.

Also notice the order. Even though we declare the non-layered style first, it's still applied after the layer styles.

HTML

<div class="box">
  <p>Hello, world!</p>
</div>

CSS

p {
  color: rebeccapurple;
}

@layer type {
  .box p {
    font-weight: bold;
    font-size: 1.3em;
    color: green;
  }
}

Result

Assigning rules to existing layers

In the following example, two layers are created with no rules applied, then CSS rules are applied to the two layers. The base layer defines a color, border, font-size, and padding. The special layer defines a different color. As special comes last when the layers were defined, the color it provides is used and the text is displayed using rebeccapurple. All of the other rules from base still apply.

HTML

<div class="item">
  I am displayed in <code>color: rebeccapurple</code> because the
  <code>special</code> layer comes after the <code>base</code> layer. My green
  border, font-size, and padding come from the <code>base</code> layer.
</div>

CSS

@layer base, special;

@layer special {
  .item {
    color: rebeccapurple;
  }
}

@layer base {
  .item {
    color: green;
    border: 5px solid green;
    font-size: 1.3em;
    padding: 0.5em;
  }
}

Result

Specifications

Specification
Unknown specification
# layering

Browser compatibility

BCD tables only load in the browser

See also