If you’re learning web development, you’ll often come across two terms: HTML (HyperText Markup Language) and XHTML (Extensible HyperText Markup Language). While they may look similar and even behave alike in many cases, there are some important differences that affect how they are written, interpreted, and validated.
Let’s break it down clearly so you can understand the differences and when to use each one.
🆚 HTML vs. XHTML – Key Differences
| Feature | HTML | XHTML |
|---|---|---|
| Case Sensitivity | Tags can be uppercase or lowercase: <HTML> or <html> | Tags must be lowercase: <html>, <body>, etc. |
| Self-Closing Tags | Not required to self-close: <br>, <img>, <hr> | Must be self-closed: <br />, <img />, <hr /> |
| Closing Tags | Optional in some cases: <p><strong></p></strong> is allowed | All tags must be properly closed and nested |
| Tag Nesting | Flexible: can close tags in any order | Strict: must close in correct order |
| Doctype Declaration | Optional or minimal declaration | Requires a full DOCTYPE declaration at the beginning |
| Error Tolerance | Browsers are forgiving of syntax errors | Strict syntax; invalid markup causes validation failure |
| Use Cases | Common for most websites | Used when strict validation or XML compatibility is needed |
🔡 1. Tag Case Sensitivity
- HTML is case-insensitive, so you can write tags like
<BODY>,<Head>, or<html>. - XHTML, on the other hand, requires all tags and attributes to be in lowercase. For example:
✅<body>❌<BODY>
🧩 2. Self-Closing Tags
In HTML, self-closing tags (those that don’t wrap content) do not need a closing slash:
<img src="logo.png">
<br>
<hr>But in XHTML, every tag must be closed — even if it doesn’t contain any content:
<img src="logo.png" />
<br />
<hr />🔁 3. Proper Tag Closure and Nesting
HTML allows a little flexibility in how tags are opened and closed:
<p><strong>This is bold text</p></strong> <!-- This works in HTML -->But XHTML enforces strict tag nesting rules — the first tag opened must be the last closed:
<p><strong>This is bold text</strong></p> <!-- Correct XHTML -->Also, in HTML, you might accidentally skip closing tags like <li>, <p>, or even <html>, and the browser will still render the page.
In XHTML, every tag must be explicitly closed, or your document will fail validation.
📄 4. Doctype Declaration
An XHTML document must begin with a DOCTYPE declaration that defines which rules it follows. For example:
XHTML 1.0 Transitional:
<!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">XHTML 1.0 Strict:
<!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">💡 Transitional allows some flexibility with HTML-style coding.
Strict requires full XHTML compliance and clean, semantic markup.
In contrast, HTML documents often use:
HTML5 Doctype:
<!DOCTYPE html>Which is much simpler and does not require defining a DTD.
📚 Summary: Which One Should You Use?
- Use HTML5 if you’re building modern websites. It’s flexible, powerful, and widely supported.
- Use XHTML only when:
- You need strict XML compliance.
- You’re integrating with systems that require well-formed XML.
- You’re validating against strict W3C standards.
🧠 Tip: XHTML is more rigid but ensures better structure. HTML is more forgiving and easier for beginners.
