Close-up photo of a chalkboard with HTML code-being written on it

While their names may sound the same, HTML, HTML5, and XHTML are three variations on the markup language HTML (Hypertext Markup Language) and are each different technologies with unique capabilities, representing evolutions of HTML throughout its lifespan as the backbone of web technology. In this article, we’ll take a quick look at the role of markup languages in web development, and how these three versions differ from one another.

What Are Markup Languages?

Markup languages are the foundation of the web—where it all started, when websites were just static pages with text and a little formatting. Essentially, everything you see on the web is a combination of markup (text), cascading style sheets or CSS (design), and front-end scripts (interactivity). That markup, made possible by HTML, is what creates a site’s foundation.

A good way to think about markup languages is as the “architecture” for a site, creating its structure and content. While programming languages like Ruby, PHP, and Python provide machines with instructions, markup languages provide computers with information. Programming languages tell data and databases how to behave; markup languages structure that data. You can learn more about the basics of markup languages in this article.


HTML was the first Internet-based language developed strictly for the web. Anything displayed in a browser is organized via HTML—it’s central to the web development process and has evolved along with it.

HTML is static structure, organization, and content—think of those early websites that were simple text with some basic formatting. The way it works is through “tags,” which tell a browser how to display specific pieces of text. At its most simple, an HTML tag tells a browser to make the selected text bold and the same goes for aligning text, creating headlines, adding hyperlinks, and more.

Once that basic HTML markup document is created, all other dynamic aspects of a site can be embedded into that file—e.g., a JavaScript program to add interactivity, server-side scripts that connect the site to the database, and CSS files that add stylistic elements. These files can all be linked out of the HTML file, making it much like the backbone of the site.

XHTML (eXtensible Hypertext Markup Language)

XHTML is essentially identical to HTML4 (the fourth iteration of HTML), but with elements of XML that extend HTML’s capabilities. XHTML came along before HTML5, right after HTML4, solving for some cross-browser compatibility issues and offering a “best of both worlds” scenario. It’s a bit stricter than HTML, providing more precise standards and specifications for how a site’s data is broken down and transmitted. This does make it a bit unforgiving, however, and it can be tougher to debug.

XHTML is written in the same format as an XML application, another descriptive markup language that functions like a complement to HTML, specifically handling how data is organized. (In markup, XML describes elements of data, while HTML displays that data.)

Much of what XHTML was designed to do has been covered with the launch of HTML5, however, making it nearly obsolete.

HTML5: The Latest and Greatest Version of HTML

HTML’s latest evolution, HTML5, is a versatile game-changer. HTML5 adds a ton of new features to the HTML repertoire, making it able to do so much more on its own. It’s a hybrid of three types of code—HTML, CSS, and JavaScript—and by bundling these three components, HTML5 lets developers work faster and more efficiently. The resulting site architecture is agile, mobile-friendly, and compatible with more browsers.

So, how else is HTML5 different from HTML? First, it touts one major advantage over its predecessor: cross-platform application development. It also solves problems that XHTML formerly addressed, and boasts better compatibility across more browsers.

HTML5 has incorporated many new APIs and features like drawing, video playback, and drag-and-drop—effects that developers could only implement before with the help of third-party plug-ins. Get the full run-down of what’s new with HTML5 in this article.

In summary…

HTML came along first, XHTML was designed to fix problems with HTML, and HTML5 solved problems XHTML was designed to fix. They’re all markup languages that provide structure and organization to the content of web pages and applications, but their relevance has shifted as newer versions of HTML have evolved, rising to the challenges of mobile demands, responsive design, and developers who want to accomplish more with less.

The Secret to Building a Team of Top-Notch Distributed Engineers

Download Now