/Web APIs

CSS Declaration

A CSS declaration is an abstract concept not exposed as an object in the DOM. It represents a CSS property and value pairing.

A CSS declaration has the following associated properties:

property name

The property name of the declaration, for example background-color.


The value of the declaration as a list of component values.

important flag

Either set or unset.

case-sensitive flag

Set if the property name is defined to be case-sensitive according to the specification, otherwise unset.

Basic example

The following example shows a CSS rule with a CSS declaration block for the <h1> element. The CSS declaration block is the lines between the curly braces, it contains two CSS declarations. One for font-style and another for color.


h1 {
  font-style: italic;
  color: rebeccapurple;


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