HTML vs. XHTML: Key Differences Explained with Examples

What Is HTML?

HTML is the standard language used to structure content on the web. It defines the structure of a web page using elements like headings, paragraphs, links, images and more.

Key Features of HTML:

Simple Syntax: HTML allows some flexibility, such as leaving out end tags for certain elements.
No Strict Case Rules: Tags can be written in uppercase, lowercase or a mix of both.
Browser Tolerance: Browsers can interpret and display poorly written or incomplete HTML code.

Example of HTML Code:

<!DOCTYPE html>
<html>
<head>
    <title>HTML Example</title>
</head>
<body>
    <h1>Welcome to HTML</h1>
    <p>This is a paragraph in HTML.</p>
</body>
</html>

What Is XHTML?

XHTML is a stricter and more standardized version of HTML, designed to improve compatibility and consistency across different systems. It follows the rules of XML (Extensible Markup Language), making it case-sensitive and less forgiving of errors.

Key Features of XHTML:

Strict Syntax: XHTML requires all tags to be properly closed and nested.
Case Sensitivity: Tags and attributes must be written in lowercase.
Improved Parsing: XHTML ensures that documents are parsed consistently across all browsers and platforms.

Example of XHTML Code:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>XHTML Example</title>
</head>
<body>
    <h1>Welcome to XHTML</h1>
    <p>This is a paragraph in XHTML.</p>
</body>
</html>

Key Differences Between HTML and XHTML

Aspect	HTML	XHTML
Case Sensitivity	Tags can be written in any case (e.g., <DIV>)	Tags must be in lowercase (e.g., <div>)
Closing Tags	Some tags can be left unclosed (e.g., <img>)	All tags must be properly closed (e.g., <img />)
Document Type	Less strict about the DOCTYPE declaration	Requires a valid DOCTYPE declaration
Error Handling	Browsers can display content even with errors	Errors prevent the page from rendering
Flexibility	More forgiving and flexible	Stricter and less forgiving
Namespace	Does not require a namespace	Requires an XML namespace declaration

Why XHTML Was Introduced

XHTML was introduced to bring the following improvements:

Consistency: Strict syntax rules ensure consistent rendering across different browsers.
Future Compatibility: Its XML-based structure prepares web pages for future technologies.
Error Handling: Enforcing proper syntax reduces potential issues in larger and more complex applications.

However, with the introduction of HTML5, the strictness of XHTML became less critical, as HTML5 brought back flexibility while incorporating modern web standards.

Practical Example: HTML vs. XHTML

HTML Version:

<!DOCTYPE html>
<html>
<head>
    <title>HTML Example</title>
</head>
<body>
    <h1>HTML Example</h1>
    <img src="image.jpg" alt="Sample Image">
    <p>This is an example using HTML.</p>
</body>
</html>

XHTML Version:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>XHTML Example</title>
</head>
<body>
    <h1>XHTML Example</h1>
    <img src="image.jpg" alt="Sample Image" />
    <p>This is an example using XHTML.</p>
</body>
</html>

Advantages of HTML

Ease of Use: More forgiving for beginners and quick development.
Widely Supported: Supported across all browsers without strict syntax requirements.
Flexibility: Allows shortcuts like omitting certain tags.

Advantages of XHTML

Standardization: Ensures cleaner and more readable code.
Better Error Handling: Discourages bad coding practices.
Consistency: XML-based rules make it easier to integrate with other XML technologies.

When to Use HTML or XHTML

Choose HTML if:
1. You prioritize flexibility and speed in development.
2. You are working on simple web pages without strict standards.
Choose XHTML if:
1. You need to integrate with XML-based systems.
2. You require strict compliance with web standards.

Current Trends: HTML5

With the introduction of HTML5, the gap between HTML and XHTML has narrowed significantly. HTML5 combines the flexibility of HTML with some of the structural improvements of XHTML, making it the preferred choice for modern web development.