HTML vs. XHTML: A Comparative Guide to Markup Languages for Web Development
HTML (Hypertext Markup Language) and XHTML (Extensible Hypertext Markup Language) are both markup languages used for creating web pages.
HTML was first introduced in the early 1990s and has undergone several revisions, while XHTML is a stricter and more modular version of HTML that was introduced in 2000 as part of the XML (Extensible Markup Language) family.
The main differences between HTML and XHTML are:
Syntax
HTML has a looser syntax than XHTML, which requires all elements to be properly nested and closed with a corresponding end tag. XHTML follows the stricter rules of XML, which requires all elements to be properly nested and closed with a corresponding end tag.
HTML Example
<p>This is a paragraph.
<p>This is another paragraph.</p>
XHTML Example
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
Case Sensitivity
HTML is not case sensitive, meaning that uppercase and lowercase tags and attributes are treated the same. XHTML is case sensitive, requiring all tags and attributes to be in lowercase.
HTML Example
<P>This is a paragraph.</P>
XHMTL Example
<p>This is a paragraph.</p>
Error Handling
HTML has more lenient error handling, allowing for errors and inconsistencies in the markup. XHTML, on the other hand, is less forgiving of errors and requires strict adherence to the markup rules.
HTML Example
<p>This is a paragraph.</p>
XHMTL Example
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
MIME Type
HTML documents are served with the MIME type "text/html", while XHTML documents are served with the MIME type "application/xhtml+xml".
Accessibility
XHTML provides better support for accessibility features such as screen readers and assistive technologies, making it a preferred choice for websites that prioritize accessibility.
HTML Example
<table border="1">
<tr>
<td>Name</td>
<td>Age</td>
</tr>
<tr>
<td>John</td>
<td>25</td>
</tr>
</table>
XHMTL Example
<table border="1">
<thead>
<tr>
<th>Name</th>
<th>Age</th>
</tr>
</thead>
<tbody>
<tr>
<td>John</td>
<td>25</td>
</tr>
</tbody>
</table>
Attribute Values
In HTML, attribute values can be enclosed in single or double quotes, while in XHTML, they must be enclosed in double quotes.
HTML Example
<img src="image.jpg" />
XHMTL Example
<img src="image.jpg" />
Entity References
XHTML requires the use of entity references for special characters, while HTML allows special characters to be included directly in the markup. For example, in XHTML, the less-than symbol "<" must be represented by the entity reference "<", while in HTML it can be included directly as "<".
HTML Example
<p>5 < 10</p>
XHTML Example
<p>5 < 10</p>
Self-Closing Tags
In XHTML, all tags must be properly closed, either with an end tag or with a self-closing slash. In HTML, some tags may be left unclosed or improperly nested.
HTML Example
<br />
XHMTL Example
<br />
Namespace
XHTML allows for the use of namespaces, which enable the creation of custom tags and attributes. HTML does not support namespaces.
HTML Example
<!DOCTYPE html>
<html>
<head>
<title>My Title</title>
</head>
<body>
<p>This is my content.</p>
</body>
</html>
XHMTL Example
<html xmlns:my="http://www.example.com/my">
<head>
<my:title>My Custom Title</my:title>
</head>
<body>
<my:content>This is my custom content.</my:content>
</body>
</html>
White Space Handling
In HTML, white space is not significant and can be used for formatting purposes. In XHTML, however, white space is significant and must be used carefully to avoid introducing errors.
HTML Example
<p>This is some text that spans multiple lines.</p>
XHMTL Example
<p>This is some text that spans multiple lines.</p>
XML Declaration
XHTML requires an XML declaration at the beginning of the document to specify the version of XML being used and the encoding of the document.
HTML Example
<!DOCTYPE html>
<html>
<head>
<title>My Title</title>
</head>
<body>
<p>This is my content.</p>
</body>
</html>
XHMTL Example
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>My Title</title>
</head>
<body>
<p>This is my content.</p>
</body>
</html>
Summary:
Both HTML and XHTML are used for creating web pages, XHTML is a stricter and more modular version of HTML that adheres to the rules of XML.
HTML is still widely used and supported by modern web browsers, and many web developers continue to use HTML for creating web pages.