HTML vs XHTML

When it comes to building web pages, the two terms "HTML" and "XHTML" often come up. While both HTML and XHTML are used to create web pages, there are important differences between the two in terms of syntax, structure, and compatibility. This chapter provides a detailed, step-by-step explanation of HTML vs. XHTML, taking you from the basics to more advanced concepts. We will explore the similarities and differences between them and demonstrate the key features with examples.

What is HTML?

HTML (HyperText Markup Language) is the standard markup language used to create web pages. It structures content on the web by using elements like headings, paragraphs, links, images, and more.

Key Features of HTML:

  • Flexibility: HTML is forgiving, meaning it tolerates minor syntax errors (e.g., missing closing tags).
  • Case-Insensitive: HTML tags are not case-sensitive, so <div> and <DIV> are treated the same.
  • Loose Syntax: HTML allows for some flexibility in how you write your code, making it easier for beginners.

Basic HTML Example

				
					<!DOCTYPE html>
<html>
<head>
    <title>HTML Example</title>
</head>
<body>
    <h1>This is an HTML Page</h1>
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</html>

Output

  • The page displays a heading saying “This is an HTML Page” and a paragraph saying “Welcome to the world of HTML!”.

What is XHTML?

XHTML (Extensible HyperText Markup Language) is a stricter version of HTML, following the rules of XML (Extensible Markup Language). It was developed to bring more consistency and structure to web development by enforcing strict rules that make code cleaner and more reliable across different platforms and devices.

Key Features of XHTML

  • Stricter Syntax: XHTML requires well-formed, valid code. All tags must be properly closed, nested, and written in lowercase.
  • Case-Sensitive: XHTML tags must be written in lowercase.
  • Self-Closing Tags: Empty elements like <br> and <img> must be self-closed with a slash (<br />, <img />).

Basic XHTML Example

				
					<!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 Example</title>
</head>
<body>
    <h1>This is an XHTML Page</h1>
    <p>Welcome to the world of XHTML!</p> <script data-no-optimize="1">/*<![CDATA[*/!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function i(t){return e({},it,t)}function o(t,e){var n,a="LazyLoad::Initialized",i=new t(e);try{n=new CustomEvent(a,{detail:{instance:i}})}catch(t){(n=document.createEvent("CustomEvent")).initCustomEvent(a,!1,!1,{instance:i})}window.dispatchEvent(n)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,bt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,bt,e)}function r(t){return s(t,null),0}function u(t){return null===c(t)}function d(t){return c(t)===vt}function f(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function _(t,e){nt?t.classList.add(e):t.className+=(t.className?" 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</html>

Output

  • The page displays a heading saying “This is an XHTML Page” and a paragraph saying “Welcome to the world of XHTML!”.

Key Differences Between HTML and XHTML

While HTML and XHTML may look similar at first glance, they differ in several important ways:

Syntax Rules

  • HTML: Syntax is flexible, and browsers often auto-correct mistakes (e.g., missing closing tags).
  • XHTML: Requires strict adherence to syntax rules. All tags must be closed, and self-closing tags must include a slash.

Example (HTML)

				
					<img data-lazyloaded="1" src="data:image/gif;base64,R0lGODdhAQABAPAAAMPDwwAAACwAAAAAAQABAAACAkQBADs=" decoding="async" data-src="image.jpg">
<p>This paragraph has no closing tag.

Example (XHTML)

				
					<img data-lazyloaded="1" src="data:image/gif;base64,R0lGODdhAQABAPAAAMPDwwAAACwAAAAAAQABAAACAkQBADs=" decoding="async" data-src="image.jpg" />
<p>This paragraph has a proper closing tag.</p>

Case Sensitivity

  • HTML: Tags are not case-sensitive, so <div> and <DIV> are treated the same.
  • XHTML: All tags must be written in lowercase.

Example (HTML)

				
					<DIV>Content goes here.</DIV>

Example (XHTML)

				
					<div>Content goes here.</div>

DOCTYPE Declaration

  • HTML: The <!DOCTYPE> declaration is used to specify the version of HTML being used. HTML5 uses a simple doctype.
  • XHTML: Requires a more complex <!DOCTYPE> declaration and an XML namespace.

Example (HTML5 Doctype)

				
					<!DOCTYPE html>

Example (XHTML Doctype)

				
					<!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">

Self-Closing Tags

  • HTML: Self-closing tags like <img> and <br> do not require a closing slash.
  • XHTML: All self-closing tags must have a slash before the closing bracket (<br />, <img />).

Example (HTML)

				
					<img data-lazyloaded="1" src="data:image/gif;base64,R0lGODdhAQABAPAAAMPDwwAAACwAAAAAAQABAAACAkQBADs=" decoding="async" data-src="image.jpg">
<br>

Example (XHTML)

				
					<img data-lazyloaded="1" src="data:image/gif;base64,R0lGODdhAQABAPAAAMPDwwAAACwAAAAAAQABAAACAkQBADs=" decoding="async" data-src="image.jpg" />
<br />

Attribute Quoting

  • HTML: Attribute values can be unquoted if they contain no spaces.
  • XHTML: Attribute values must always be enclosed in quotes.

Example (HTML)

				
					<input type=text value=Submit>

Example (XHTML)

				
					<input type="text" value="Submit" />

Error Handling

  • HTML: Browsers are lenient with errors and attempt to fix invalid HTML code automatically.
  • XHTML: Browsers will fail to render the page if there are any syntax errors.

Namespace

  • HTML: Does not require the use of an XML namespace.
  • XHTML: Requires the inclusion of an XML namespace (xmlns).

Example

				
					<html xmlns="http://www.w3.org/1999/xhtml">

When to Use HTML vs. XHTML?

Use HTML

  • When you need a flexible, forgiving language for web development.
  • For most modern web applications, especially since HTML5 is widely adopted and supports a wide range of features.
  • When backward compatibility with older browsers is essential.

Use XHTML

  • When strict syntax is required, such as in environments where XHTML documents must be parsed as XML.
  • For applications where consistency and well-formedness are critical, like in mobile web applications.
  • If your project relies on XML-based processing.

HTML5: The Evolution

With the advent of HTML5, many features that XHTML brought to the table are now part of the standard HTML. HTML5 allows for more structured and semantic coding while maintaining backward compatibility with older HTML standards.

Key Features of HTML5

  • Simpler Syntax: HTML5 allows for a more straightforward and less strict syntax compared to XHTML.
  • Support for New Elements: HTML5 introduced new elements like <article>, <section>, and <footer>, which provide more semantic meaning.
  • Self-Closing Tags Optional: In HTML5, self-closing tags are no longer mandatory, although browsers still support XHTML-style self-closing tags.

Example

				
					<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>HTML5 Example</title>
</head>
<body>
    <section>
        <h1>HTML5 vs XHTML</h1>
        <p>HTML5 brings modern features with simpler syntax.</p>
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In conclusion, while both HTML and XHTML serve similar purposes in creating web pages, XHTML enforces stricter syntax rules and is more closely aligned with XML. HTML is more flexible and forgiving, especially with the advent of HTML5, which brings a balance between structure and flexibility.Happy coding !❤️

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