In this article, we will examine HTML XHTML. A stricter version of HTML, known as XHTML, is based on XML and uses many more XML tags and elements.

What is XHTML?

  1. It is an acronym for Extensible HyperText Markup Language.
  2. The XHTML specification is a stricter version of HTML based on XML
  3. HTML is defined as an XML application in XHTML
  4. All major browsers support XHTML


Documents in XML must be adequately marked up (be “well-formed”).

A browser will also display the website even with errors in HTML markup when it has errors in HTML. In other words, XHTML has a much stricter error-handling system.

It was developed to make HTML more extensible and flexible (so it could be used in conjunction with XML, for example).

What makes HTML different from XHTML.

  1. <!DOCTYPE> must be specified.
  2. HTML must contain the xmlns attribute.
  3. <html>, <head>, <title>, and <body> must be included.
  4. Lowercase elements are always required.
  5. Lowercase is required for all attribute names.
  6. Quote all attribute values.
  7. There is no room for attribute minimization.
  8. A properly nested element is always required.
  9. Ensure that all elements are closed.

XHTML – <!DOCTYPE ….> Is Mandatory

To be considered HTML XHTML, the document must have an XHTML <DOCTYPE> declaration.

A document must also contain the <html>, <head>, <title>, and <body> tags, and the xmlns attribute in the HTML must specify the xml namespace.

This XHTML document contains the bare minimum of tags needed:


<!DOCTYPE html> <html xmlns=""> <head><title>Title of example document</title> </head> <body>some content here…</body> </html>

XHTML Elements Must be Properly Nested

The following is an example of proper nesting of elements in XHTML when it comes to HTML XHTML:

  Correct Syntax

<!DOCTYPE html> <html><body><br><br><br><b><br><i>Keep eye on opening and closing tags</i><br></b><br><br> </body></html>


Wrong Syntax

<!DOCTYPE html >
<html><body><b><i>Keep eye on opening and closing tags</i></b></body></html>

XHTML Elements Must Always be Closed

A closed element in XHTML must look like this:


<!DOCTYPE html> <html><body><br><br><br><p>This is a paragraph with closing tag.</p><br><p>This is another paragraph with closing tag.</p><br><br> </body></html>


<!DOCTYPE html> <html><body><br><br><br><p>This is a paragraph without closing tag.<br></p><br><p>This is another paragraph without closing tag.</p><br><br> </body></html>

XHTML Empty Elements Must Always be Closed

When we talk about HTML XHTML then, XHTML requires empty elements to be closed, as follows:

  Correct Way

<!DOCTYPE html> <html><body><br><br><br><p>A break line: <br>A horizontal rule: </p><br><hr><br>An image src: <img src="" alt="Sad face"> </body></html>

  Wrong Way

<!DOCTYPE html> <html><body><br><br><br><p>A break line: <br>A horizontal rule: </p><hr><br>An image: <img src="" alt="Sad face"><br> </body></html>

Lowercase is required for XHTML

It is always necessary to use lowercase names for element names in XHTML, as shown here:

  Correct Syntax

<!DOCTYPE html> <html><body><br><br><br><p>All tags are in small letters</p><br><br> </body></html>

  Wrong Syntax

<!DOCTYPE html> <html><body><br><br><br><p>All tags are in capital letters</p><br><br> </body></html>

Attribute names must be lowercase in XHTML

It is mandatory to always write attribute names in lowercase in XHTML, such as this:

  Correct Syntax

<!DOCTYPE html> <html><body><br><br><br><a href="">Attibute href is in small letter's.</a><br><br><br> </body></html>

  Wrong Syntax

<!DOCTYPE html> <html><body><br><br><a href=""><br>Attibute href is in capital letter's.</a><br><br> </body></html>

Quote all XHTML attribute values

To use XHTML, attribute values must be quoted in the following way as it comes to HTML XHTML:

  Correct Method

<!DOCTYPE html> <html><body><br><br><br><a href="">Mr example link is inside quotation marks</a><br><br> </body></html>

  Wrong Method

<!DOCTYPE html> <html><body><br><a href="">Mr example link without quotation marks</a><br> </body></html>

Attribute minimization in XHTML

The following attributes are not allowed to be minimized in XHTML:

  Correct Syntax

<!DOCTYPE html> <html><body><br><br><br><input type="checkbox" name="electric" value="car" checked><br><input type="text" name="lastname" disabled><br> </body></html>

Example:  Incorrect Syntax

<!DOCTYPE html> <html><body><br><br><br><input type="checkbox" name="Electric" value="car" checked><br><input type="text" name="lastname" disabled><br> </body></html>

Advantages of XHTML Versus HTML

XHTML (Extensible Hypertext Markup Language) and HTML (Hypertext Markup Language) are both markup languages used for creating web pages. XHTML is a stricter and more standardized version of HTML. Here are some advantages of XHTML over HTML:

  1. Well-Formedness: XHTML documents must be well-formed, meaning that they follow a strict set of rules for syntax and structure. This makes it easier to write and maintain web pages and helps to avoid errors.
  2. Consistency: Because XHTML is a more standardized version of HTML, it provides greater consistency across different web browsers and devices. This means that web pages will look more consistent across different platforms.
  3. XML-based: XHTML is based on the XML (Extensible Markup Language) standard, which allows for greater flexibility and extensibility. This means that web developers can create their own custom tags and attributes.
  4. Compatibility: XHTML is backward compatible with HTML, meaning that XHTML documents can be displayed in web browsers that support HTML. This makes it easy to transition from HTML to XHTML.
  5. Accessibility: XHTML provides better support for accessibility features, such as screen readers, than HTML. This makes it easier for people with disabilities to access web content.

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