What is XHTML & How Does it Differ From HTML?

Athena Ozanich
Athena Ozanich


The X-Men are to humans as XHTML is to HTML. That is to say, many consider it the next step in the evolution of the future of web browser markup language. Learning what it is and how it can improve your website development can have a string of benefits for your organization.

A young woman studies XHTML and how she can utilize it to benefit her workflow.

This post will cover the purpose and benefits of using XHTML. Furthermore, you will discover the difference between standard HTML and XHTML, as well as the similarities. You will also see some code examples XHTML, showcasing both the correct and incorrect syntax.

Let’s get started.

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What is XHTML?

To understand XHTML, you inevitably need to understand HTML since it is an extension of that language. But it is also an extension of the XML language; that is to say, it is more like a cross of the two languages.

The primary goal of XHTML is to create a stricter way to develop websites consistently and expectantly. XHTML works by allowing you to write standard HTML using the strict guidelines of the XML format.

It's also worth considering that HTML should not be confused with HTML5 as they are different. HTML5 has largely replaced XHTML and is often considered to be the superior choice.

Let’s look at the comparison between XHTML and HTML.


There isn’t much difference in how they look and behave, other than the strict syntax. Let’s look at an example of code that shows the difference between strictness and syntax between the two languages.

In HTML, the syntax for creating a basic page is less rigid, and incorrect HTML syntax will often be compensated for by the browser. All modern browsers will try to fix broken HTML within limitations, such as closing an unclosed tag or assuming values for missing attributes.

Let’s look at that first with an example of a basic webpage missing tags altogether.

        Title of document
    some content here...

The code above is missing vital tags such as the doctype and a closing body tag. This is not correct syntax and should cause an error. However, most browsers will attempt to assume the necessary information to render the page and items correctly. Check out the next video to learn more about XHTML and HTML differences.

With XHTML, these syntax errors would throw errors and instead not correctly render pages or items. The XHTML required to complete the above page would look something like the code below.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
            Title of document
            some content here...

The above information is required in order to have an error-free page.


The value behind XHTML is evident when you consider the industry standards and requirements it enforces, which leads to better development practices. Furthermore, many of the industry standards are meant to increase security and performance.

Enforcing these standards creates a more consistent web experience for users across browsers for both the design and user experience.

Next, let’s look at some examples of correct versus incorrect syntax of XHTML code and further explore how it differs from standard HTML.

XHTML Example

The best way to learn how to properly understand XHTML is to learn the rules it enforces; in that vein, the following code snippets will explore the rules.

An XHTML document must have an XHTML <!DOCTYPE> declaration, <html>, <head>, <title>, and <body> elements must also be present, and the xmlns attribute in <html> must specify the xml namespace for the document. The code above showcases these rules; the code below will look at some of the other rules XHTML enforces.

In XHTML, elements must always be properly nested and closed, as shown below:

<p><b>Some text</b></p>

Writing out the above code with the tags improperly nested or closed will cause validation errors. This is also true of empty elements like the image tag.

<p><b>Some text</p></b>

<p><b>Some text</b>

The above two lines would cause an error, the first because the closing tags are in the wrong order, the second because there is a missing closing tag. Furthermore, XHTML is case-sensitive, and using any uppercase letters will also cause validation errors. <P><b>Some text</b></P> The above code would throw validation errors due to the uppercase paragraph tag, this case sensitivity also applies to the HTML attributes. This means HTML attributes such as the href attribute must be declared in a lowercase letter to avoid validation errors. Finally, HTML attributes cannot be used in their minimized form, which will also cause validation errors.

<input type="text" name="lastname" disabled/>

The above code would cause an error. Instead, you would expand the disabled attribute to its full form, as shown below.

<input type="text" name="lastname" disabled="disabled"/>

Getting Started With XHTML

There isn’t much to learn about XHTML, and this post covers almost everything you need to get started using it. However, it is worth noting that the introduction of HTML5 has largely outgrown the use of XHTML, and most developers favor it over the former.

The introduction of HTML5 saw the strictness of XML enforced while offering the benefits of new tags and many other performance-enhancing features. The choice of which to use is largely up to you; just be sure to do the research required to understand which is the best fit for you.

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