revert-layer

The revert-layer keyword lets you rollback styles to those specified in previous cascade layers within the author origin. The revert keyword, in comparison, lets you roll back styles applied in the author origin to those specified in the user origin or user-agent origin.

The revert-layer keyword is ideally meant to be applied to properties within a cascade layer. However, if applied to properties outside a cascade layer, it rolls back property values to any values set by presentational hints (such as width and height attributes or the <s> element in HTML), defaulting to the values established by the user agent's stylesheet or user styles. Unlike the revert keyword, which considers presentational hints as part of the author origin and reverts them as well, the revert-layer keyword ignores presentational hints outside the cascade layer, so it does not revert them.

In the example below, two cascade layers are defined in the CSS, base and special. By default, rules in the special layer will override competing rules in the base layer because special is listed after base in the @layer declaration statement.

HTML

<p>This example contains a list.</p>

<ul>
  <li class="item feature">Item one</li>
  <li class="item">Item two</li>
  <li class="item">Item three</li>
</ul>

CSS

@layer base, special;

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

@layer base {
  .item {
    color: blue;
  }
  .feature {
    color: green;
  }
}

Result

All the <li> elements match the item rule in the special layer and are red. This is the default cascade layer behavior, where rules in the special layer take precedence over rules in the base layer.

Let's examine how the revert-layer keyword changes the default cascade layer behavior. For this example, the special layer contains an additional feature rule targeting the first <li> element. The color property in this rule is set to revert-layer.

HTML

<p>This example contains a list.</p>

<ul>
  <li class="item feature">Item one</li>
  <li class="item">Item two</li>
  <li class="item">Item three</li>
</ul>

CSS

@layer base, special;

@layer special {
  .item {
    color: red;
  }
  .feature {
    color: revert-layer;
  }
}

@layer base {
  .item {
    color: blue;
  }
  .feature {
    color: green;
  }
}

Result

With color set to revert-layer, the color property value rolls back to the value in the matching feature rule in the previous layer base, and so 'Item one' is now green.

This example shows the revert-layer keyword behavior when there is no cascade layer to revert to and there is no matching CSS rule in the current layer to inherit the property value.

HTML

<p>This example contains a list.</p>

<ul>
  <li class="item feature">Item one</li>
  <li class="item">Item two</li>
  <li class="item">Item three</li>
</ul>

CSS

@layer base {
  .item {
    color: revert-layer;
  }
}

Result

The style for all <li> elements rolls back to the defaults in the user-agent origin.

• initial
• inherit
• revert
• unset
• all
• CSS cascade and inheritance module