HTML Id

The HTML id attribute is used to specify a unique id for an HTML element.

You cannot have more than one element with the same id in an HTML document.

The id Attribute

The id attribute specifies a unique id for an HTML element. The value of the id attribute must be unique within the HTML document.

The id attribute is used to point to a specific style declaration in a style sheet. It is also used by JavaScript to access and manipulate the element with the specific id.

The syntax for id is: write a hash character (#), followed by an id name. Then, define the CSS properties within curly braces {}.

In the following example we have an <h1> element that points to the id name "myHeader". This <h1> element will be styled according to the #myHeader style definition in the head section:

Example

Note: The id name is case sensitive!

Note: The id name must contain at least one character, cannot start with a number, and must not contain whitespaces (spaces, tabs, etc.).

Difference Between Class and ID

A class name can be used by multiple HTML elements, while an id name must only be used by one HTML element within the page:

Example

Tip: You can learn much more about CSS in our CSS Tutorial.

HTML Bookmarks with ID and Links

HTML bookmarks are used to allow readers to jump to specific parts of a webpage.

Bookmarks can be useful if your page is very long.

To use a bookmark, you must first create it, and then add a link to it.

Then, when the link is clicked, the page will scroll to the location with the bookmark.

Example

First, create a bookmark with the id attribute:

Example

Then, add a link to the bookmark ("Jump to Chapter 4"), from within the same page:

Example

<a href="#C4">Jump to Chapter 4</a>

Or, add a link to the bookmark ("Jump to Chapter 4"), from another page:

Example

<a href="html_demo.html#C4">Jump to Chapter 4</a>

Using the id Attribute in JavaScript

The id attribute can also be used by JavaScript to perform some tasks for that specific element.

JavaScript can access an element with a specific id with the getElementById() method:

Example

<script>
function displayResult() {
  document.getElementById("myHeader").innerHTML = "Have a nice day!";
}

  </script>

Tip: Study JavaScript in the HTML JavaScript chapter, or in our JavaScript Tutorial.

Chapter Summary

• The id attribute is used to specify a unique id for an HTML element

• The value of the id attribute must be unique within the HTML document

• The id attribute is used by CSS and JavaScript to style/select a specific element

• The value of the id attribute is case sensitive

• The id attribute is also used to create HTML bookmarks

• JavaScript can access an element with a specific id with the getElementById() method

Video: HTML ID