ID Selector

Another selector is the ID selector. Similar to classes, let's look at the following code:

<h1 id="identifier">Title</h1>

This code contains an h1 element with the id attribute set to identifier. We say that this element has the ID identifier.

In HTML, multiple elements cannot have the same ID. To select an element with a specific ID in CSS, we use the selector #identifier as follows:

#identifier {
	background-color: blue;
}

Similar to class selectors, the ID selector starts with a symbol, in this case, #. It indicates that we want to select an HTML element with a specific ID, in this case, the ID identifier.