Using Same Id for Multiple HTML Tags

Can multiple different HTML elements have the same ID if they’re different elements?

Element IDs should be unique within the entire document.

What error will i get if i use the same ID for multiple HTML elements?

In some environments, it may produce a console warning that multiple IDs in a single document is invalid. Harmless, but annoying.

It will prevent document.getElementById from working properly for those elements, because getElementById selects by ID, but there should only be one element with a given ID in the document. Similarly, it may prevent querySelector and querySelectorAll with ID selectors from working properly.

Using the same ID multiple times may well not break your application in most cases, but just because it might be doable in some circumstances doesn’t mean it’s a good idea. There’s no reason to do it, so don’t.

Can multiple HTML tags have the same ID if they are on different files?

The id must be unique inside one file but not across different files (as long as not one file includes the other).

Can you use the same id once for multiple html page?

An id should only be used once on a single document. It is used for elements that only should appear once on the page anyway (think of a «top navigation bar»). Classes are used for elements that can appear more than once (think of a «particularly styled table», a «repeatable block of information» or things that share particular charasteristics such as «on this browser width this block spans 6 columns» in for example bootstrap). It is perfectly normal to use the same id on different pages. Usually you’ll make a skeleton/template for your layout, where each element will be styled the same on each page that uses this template. It is then helpful to have the same id for the same element across different pages. (or: It would be considered sloppy to change the layout of the page on every page, using different id’s for each element, as it would be hard or impossible to maintain your pages.)

Dealing with Two Elements with same ID in JavaScript

I know that IDs should be unique, however, I have to deal with a page
that has two elements with the exact same ID

As you’ve stated it should be unique hence if you have more than one id attribute with the same name then that’s not valid HTML.

How can I access the second element with the exact same ID as the
first in JavaScript?

wouldn’t it be easier to use getElementsByClassName since having two id attributes with the same name is invalid HTML?.

with that in mind, you can use getElementsByClassName .That may be more suited to your requirements.

var x = document.getElementsByClassName("Design_01"); // x is an array
var firstElement = x[0]; // get first element
var secondElement = x[1]; // get second element

Relevant Readings:

• HTML DOM getElementsByClassName() Method
• JavaScript Arrays

Can two html elements have the same id but in different classes?

Possible? Yes.
Good coding? No.

ID and NAME tokens must begin with a letter ([A-Za-z]) and may be
followed by any number of letters, digits (6), hyphens («-«),
underscores («_»), colons («:»), and periods («.»).

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HTML id Attribute

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.

Using 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 element that points to the id name «myHeader». This 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

/* Style all elements with the class name «city» */
.city background-color: tomato;
color: white;
padding: 10px;
>

London is the capital of England.

Paris is the capital of France.

Tokyo is the capital of Japan.

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:

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

Example

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

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

Use the id attribute to manipulate text with JavaScript:

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

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Can Multiple Different HTML Elements Have the Same Id If They’Re Different Elements

Can multiple different HTML elements have the same ID if they’re different elements?

Element IDs should be unique within the entire document.

What error will i get if i use the same ID for multiple HTML elements?

In some environments, it may produce a console warning that multiple IDs in a single document is invalid. Harmless, but annoying.

It will prevent document.getElementById from working properly for those elements, because getElementById selects by ID, but there should only be one element with a given ID in the document. Similarly, it may prevent querySelector and querySelectorAll with ID selectors from working properly.

Using the same ID multiple times may well not break your application in most cases, but just because it might be doable in some circumstances doesn’t mean it’s a good idea. There’s no reason to do it, so don’t.

Can multiple HTML tags have the same ID if they are on different files?

The id must be unique inside one file but not across different files (as long as not one file includes the other).

Can two html elements have the same id but in different classes?

Possible? Yes.
Good coding? No.

ID and NAME tokens must begin with a letter ([A-Za-z]) and may be
followed by any number of letters, digits (4), hyphens («-«),
underscores («_»), colons («:»), and periods («.»).

Can you use the same ID with different element types in CSS?

I know this is invalid HTML

Yes. An ID must be unique in the document. Not unique per type in the document.

(That won’t stop browser error recovery from sometimes giving you the result you are trying to achieve, but you should not depend on that).

You can’t use .# . A . starts a class selector. A # starts an ID selector.

And then have two different documents, one with a div with that ID and one with a paragraph with that ID, but both of which to the same stylesheet.

If you want to identify two things are being in a group, then use a class. That is what class is for.

Can same id address multiple elements in html?

It would be much, much better, in terms of both validity and semantics, if you wrote it using classes for your CSS instead:

.p01 color: blue;
>

Heading

This is a paragraph.

This is a diff paragraph.

This is a paragraph.

I am different.

Just because it works using id doesn’t mean that it’s correct. Imagine in a month that you want to add some javascript to get only one of those elements, you couldn’t then use this:

var e = document.getElementById("p01");

because you couldn’t be certain of what would be returned.

One way to look at it is by thinking of houses. Imagine that classes define the types of houses (apartments, bungalows, houses with pitched roofs etc), whereas ids define specific houses (John’s house, Wendy’s house etc).

Now imagine that you want to have all the bungalows painted red. Using the class, you can easily grab all of them at once, like:

var houses = document.getElementsByClassName("bungalow");
paint_red(houses);

Now imagine that you want to send a package to Wendy’s house. In this case, you can find that specific house using its id:

var wendys_house = document.getElementById("wendy");
send_package_to(wendys_house);

Because you know that the id is unique, you can be certain that only Wendy’s house will receive a package.

Dealing with Two Elements with same ID in JavaScript

I know that IDs should be unique, however, I have to deal with a page
that has two elements with the exact same ID

As you’ve stated it should be unique hence if you have more than one id attribute with the same name then that’s not valid HTML.

How can I access the second element with the exact same ID as the
first in JavaScript?

wouldn’t it be easier to use getElementsByClassName since having two id attributes with the same name is invalid HTML?.

with that in mind, you can use getElementsByClassName .That may be more suited to your requirements.

var x = document.getElementsByClassName("Design_01"); // x is an array
var firstElement = x[0]; // get first element
var secondElement = x[1]; // get second element

Relevant Readings:

• HTML DOM getElementsByClassName() Method
• JavaScript Arrays

Can multiple different HTML elements have the same ID if they’re different elements?

Element IDs should be unique within the entire document.

Can an HTML element have multiple ids?

No. From the XHTML 1.0 Spec

In XML, fragment identifiers are of
type ID, and there can only be a
single attribute of type ID per
element. Therefore, in XHTML 1.0 the
id attribute is defined to be of type
ID. In order to ensure that XHTML 1.0
documents are well-structured XML
documents, XHTML 1.0 documents MUST
use the id attribute when defining
fragment identifiers on the elements
listed above. See the HTML
Compatibility Guidelines for
information on ensuring such anchors
are backward compatible when serving
XHTML documents as media type
text/html.

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