HTML vs. XHTML

⚖️ HTML vs. XHTML

XHTML is HTML written as XML. It follows stricter syntax rules than HTML and requires well-formed documents. While HTML is more forgiving, XHTML demands precision in every tag and attribute.


<!-- HTML: More forgiving -->
<p>This is a paragraph
<br>
<img src="image.jpg" alt="Image">

<!-- XHTML: Strict XML rules -->
<p>This is a paragraph</p>
<br />
<img src="image.jpg" alt="Image" />

Key Differences

📝

HTML Syntax

Flexible and forgiving syntax

<!DOCTYPE html>
<html>
<head>
  <title>HTML Page</title>
</head>
<body>
  <P>Uppercase tags OK</P>
  <p>Unclosed paragraph
  <br>
  <img src="pic.jpg" alt="Image">
</body>
</html>

Features: Case-insensitive, optional closing tags, forgiving

⚡

XHTML Syntax

Strict XML-compliant syntax

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>XHTML Page</title>
</head>
<body>
  <p>All lowercase tags</p>
  <br />
  <img src="pic.jpg" alt="Image" />
</body>
</html>

Features: Case-sensitive, all tags must close, strict

🔍

Tag Rules

Different rules for writing tags

<!-- HTML: Flexible -->
<P>Uppercase OK</P>
<p>Mixed case OK</P>
<br>
<input type="text">

<!-- XHTML: Strict -->
<p>lowercase only</p>
<br />
<input type="text" />

XHTML Rules: Lowercase tags, close empty elements, quote attributes

🌐

Browser Support

How browsers handle each format

HTML:

Universal browser support
Error-tolerant parsing
Faster rendering

XHTML:

Requires XML parser
Strict error handling
One error breaks page

🔹 XHTML Strict Rules

XHTML enforces several strict rules that HTML doesn't require:

XHTML Requirements:

All tags must be lowercase: not
All tags must be closed: text
Empty tags must be self-closed: not
All attributes must be quoted: class="example"
All attributes must have values: checked="checked"
Proper nesting required: No overlapping tags

🔸 Correct vs Incorrect Examples

<!-- ❌ WRONG in XHTML -->
<P>Uppercase tag</P>
<p>Unclosed paragraph
<br>
<img src=image.jpg alt=Image>
<input type=text checked>

<!-- ✅ CORRECT in XHTML -->
<p>Lowercase tag</p>
<br />
<img src="image.jpg" alt="Image" />
<input type="text" checked="checked" />

🔹 Practical Comparison

See the differences in real examples:

🔸 Form Elements

<!-- HTML Version -->
<form action=/submit method=post>
  <input type=text name=username required>
  <input type=checkbox name=agree checked>
  <input type=submit value=Submit>
</form>

<!-- XHTML Version -->
<form action="/submit" method="post">
  <input type="text" name="username" required="required" />
  <input type="checkbox" name="agree" checked="checked" />
  <input type="submit" value="Submit" />
</form>

🔸 Media Elements

<!-- HTML Version -->
<img src=photo.jpg alt="My Photo" width=300 height=200>
<hr>
<br>

<!-- XHTML Version -->
<img src="photo.jpg" alt="My Photo" width="300" height="200" />
<hr />
<br />

🔹 Which Should You Use?

Choose HTML5 if:

Building modern web applications
Want faster development
Need maximum browser compatibility
Working with dynamic content

Choose XHTML if:

Working with XML-based systems
Need strict document validation
Integrating with XML workflows
Maintaining legacy XHTML sites

💡 Recommendation:

Use HTML5 for new projects. It's the current standard, more flexible, and has better browser support. XHTML is mainly used for specific XML integration scenarios.