HTML id Attribute

HTML <track>

HTML <ul>

An id on a tag assigns an identifier to the element.

The identifier must be unique across the page.

Example

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An id attribute on a tag.

This text is underlined.

<p>
  <u id="u-id">This text is underlined</u>.
</p>

Using id

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The id attribute assigns an identifier to the element.

The id allows JavaScript to easily access the element.

It is also used to point to a specific id selector in a style sheet.

Tip: id is a global attribute that can be applied to any HTML element.

Syntax

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<u id="identifier" />

Values

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Value	Description
identifier	A unique alphanumeric string. The id value must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens (-), underscores (_), colons (:), and periods (.).

More Examples

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A element with a unique id.
Clicking the button displays the text in the element.

This text is underlined.

<p>
  <u id="myu">This text is underlined</u>.
</p>
  
<br />
<button onclick="show();">Show underlined text</button>

<script>
  let show = () => {
     let element = document.getElementById("myu");
     alert("Text = " + element.innerHTML);
  }
</script>

Code explanation

The id attribute assigns a unique identifier for the .

Clicking the button calls JavaScript which locates the using the id.

Finally, the content of the element is displayed in an alert box.

Browser support

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Here is when id support started for each browser: