HTML (Hypertext Markup Language) and XHTML (Extensible Hypertext Markup Language) are both markup languages used to structure content on the web. While they share similarities, there are key differences between the two:
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Syntax and Document Structure:
- HTML: HTML has a more lenient syntax and is forgiving of errors. Tags can be written in uppercase or lowercase, and unclosed tags are often tolerated by browsers.
- XHTML: XHTML follows a stricter syntax and is more unforgiving of errors. Tags must be written in lowercase, and documents must be well-formed XML, meaning that tags must be properly nested and closed.
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Document Declaration:
- HTML: HTML documents start with a <!DOCTYPE html> declaration, and the syntax is generally simpler.
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XHTML:
XHTML documents start with an XML declaration, and they require a more specific Document Type Definition (DTD), such as
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">.
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Tag Closure:
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HTML:
In HTML, certain tags, such as
<img>, <br>, and <hr>, don't require explicit closing tags. It is common to write them as self-closing (<img src="example.jpg" />).
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HTML:
In HTML, certain tags, such as
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Attribute Quotation:
- HTML: Attribute values can be quoted or unquoted in HTML, and both single and double quotes are accepted.
- XHTML: Attribute values must be enclosed in double or single quotes.
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Parsing Rules:
- HTML: HTML browsers are more forgiving of syntax errors and may render pages even if the markup is not entirely correct.
- XHTML: XHTML requires well-formed documents, and browsers are less forgiving. A minor syntax error can lead to a failure in rendering the entire page.
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Error Handling:
- HTML: HTML is more forgiving of errors, and browsers attempt to render the page even if there are issues with the markup.
- XHTML: XHTML has stricter error handling, and browsers may display an error message or refuse to render the page if the document is not well-formed.
In summary, while HTML is more forgiving and lenient in its syntax, XHTML adheres to a stricter set of rules borrowed from XML. The choice between HTML and XHTML depends on the specific requirements of a project and the preference of the developer or organization. In modern web development, HTML5 has become the standard, incorporating some of the flexibility of HTML and introducing new features, rendering the distinction between HTML and XHTML less relevant for many developers.
