HTML
HTML Versus XHTML
Web developers use HTML and XHTML to build web pages. Both formats define page content and layout but follow different rules. This tutorial explains those key differences. You will learn how to write in each format and see clear examples to guide your work.
Learning Outcomes
After reading this tutorial, you will be able to:
- Identify the main syntax differences between HTML and XHTML
- Explain how browsers handle errors in HTML versus XHTML
- Apply correct nesting and closing rules in XHTML
- Convert tag and attribute names to lowercase for XHTML
- Wrap every attribute value in quotes for valid XHTML
What is HTML?
HTML (Hypertext Markup Language) is the standard markup language used to create and structure content on the web. It uses tags to define elements like headings, paragraphs, links, and images. HTML provides the foundational structure for any web page, enabling web browsers to interpret and display content. HTML is known for its flexibility and relatively lenient rules, which makes it beginner-friendly and quick to implement.
Pros
- HTML tags follow a clear pattern, making it easy to learn
- All browsers support HTML
- Pages still load despite minor mistakes in HTML
- HTML works on any operating system
Cons
- Browsers hide syntax errors, causing unexpected results
- HTML lacks strict rules to prevent insecure code
- HTML does not support some emerging web features
What is XHTML?
XHTML ****(Extensible Hypertext Markup Language) is a stricter and more standardized version of HTML that incorporates rules from XML (Extensible Markup Language). XHTML was designed to fix the errors inherent in HTML, especially its loose syntax. The key difference is that XHTML follows more stringent rules, making it more robust and future-proof for web applications and devices.
Pros
- Enforced syntax produces cleaner and more consistent code
- Strict rules improve page security
- XML compliance lets you convert pages into formats like RSS or SOAP
- High portability makes pages work well on low-power devices
Cons
- Strict rules increase complexity and learning time
- Some browsers do not fully support XHTML
- Any syntax error prevents the page from loading
Key Characteristics of XHTML
- Every document includes a DOCTYPE declaration that specifies its XHTML version
- Tags always nest correctly (for example,
<b><i>Text</i></b>) - Empty elements always close themselves (for example,
<img src="image.jpg" />) - Tag names and attribute names use lowercase letters
- Every attribute value uses quotation marks (for example,
<a href="https://example.com">) - Attributes always include explicit values (for example,
checked="checked")
Similarities Between XHTML and HTML
| Feature | HTML & XHTML |
|---|---|
| Basic Purpose | Both are used to create web pages and applications. XHTML enforces stricter rules. |
| Multimedia Support | Both support images, videos, and audio. |
| Styling Support | Both support CSS for styling. |
| Scripting Support | Both support JavaScript for interactivity. |
| Form Elements | Both support input forms for user interaction. |
| Linking Support | Both support anchor links to navigate between pages. |
| Document Structure | Both use the same basic structure (<html>, <head>, <body>), but XHTML is stricter. |
| Compatibility with Browsers | Both are supported by most modern browsers; however, some older browsers may not fully support XHTML. |
Differences Between HTML and XHTML
| Feature | HTML | XHTML |
|---|---|---|
| Full Form | Hypertext Markup Language | Extensible Hypertext Markup Language |
| Case Sensitivity | Not case-sensitive | Case-sensitive, all tags must be lowercase |
| DOCTYPE | Optional | Mandatory |
| Closing Tags | Not mandatory | All tags must be closed |
| Nesting Rules | Flexible | Strict nesting rules |
| Attribute Quotes | Not required | Attribute values must be quoted |
| Error Handling | Errors don't stop rendering | Errors prevent page from rendering |
| Security | Less secure | More secure |
| Browser Support | Supported by all browsers | Limited support by older browsers |
| Syntax | Looser syntax | Stricter syntax, follows XML rules |
How to Migrate from HTML to XHTML
- Ensure tags nest correctly and all elements close (for example,
<p><strong>Text</strong></p>) - Add the correct DOCTYPE at the top of the document (for example,
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">) - Convert every tag name and attribute name to lowercase (for example,
<a href="link.html">) - Wrap every attribute value in double quotes (for example,
alt="Description")
How to Migrate from XHTML to HTML
- Convert self-closing tags such as
<br />into<br> - Replace the XHTML DOCTYPE with
<!DOCTYPE html> - Use uppercase or lowercase tags freely since HTML ignores case
- Remove quotes around simple attribute values but keep them when needed for clarity
FAQs on XHTML and HTML
Why Use XHTML Instead of HTML?
XHTML enforces a stricter, more organized syntax that reduces errors and is more secure. It is also easier to convert to other formats, such as XML.
Is XHTML Used Anymore?
XHTML has largely been replaced by HTML5, as HTML5 offers more flexibility and broader browser support. However, some legacy projects may still use XHTML for specific needs.
Where Is XHTML Used?
XHTML is typically used in situations where stricter code standards are necessary, such as in web services, XML-based formats, or when integrating with other XML applications.
Do Browsers Support XHTML?
Most modern browsers support XHTML, but older browsers may not render it correctly. HTML5 is now the preferred choice for modern web development due to its extensive browser support and flexibility.