markup language which places HTML in XML form

XHTML stands for eXtensible HyperText Markup Language. It is markup used to design websites and webpages.

Filename extension.xhtml, .xht,
.xml, .html, .htm
Internet media typeapplication/xhtml+xml
Developed byWorld Wide Web Consortium
Initial release26 January 2000 (2000-01-26)
Latest release
(28 October 2014; 9 years ago (2014-10-28))
Type of formatMarkup language
Extended fromXML, HTML
StandardW3C HTML5 (Recommendation)
Open format?Yes

XHTML is much more strict than ordinary HTML, and is based on both XML and HTML. Due to the lax nature of HTML, different web browsers can sometimes display websites incorrectly since there is more than one way to interpret poorly written HTML. The strict and formal nature of XHTML, once fully adopted will allow for web browsers to display the same page correctly between them. Proper XHTML is also easier to read for humans.

For example, the below code shows one of the differences between HTML and XHTML:

Incorrect, HTML version:


Correct, XHTML version:

<br />

The line break tag in HTML does not have a closing tag, you just type it once and it creates a line break. In XHTML the rule is that tags that do not have an closing tag must close themselves within the initial tag. These tags are called "empty tags." Another empty tag is <hr /> which inserts a "horizontal rule" or dividing line.

JavaScript Differences


In XHTML, using innerHTML is not "allowed". XHTML also should not be used together with the JavaScript document.write command.