HTML (Hypertext Markup Language) and XHTML (Extensible Hypertext Markup Language) are both markup languages used to structure and present content on the web. While they share many similarities, there are key differences between HTML and XHTML:
Syntax:
HTML: HTML has a more lenient syntax, allowing for certain deviations and omissions. For example, in HTML, it is common to have unclosed tags or attribute values without quotes.
XHTML: XHTML has a stricter syntax and follows the rules of XML. All tags must be properly nested and closed, and attribute values must be enclosed in quotes. XHTML is case-sensitive, requiring tags and attributes to be written in lowercase.
Document Structure:
HTML: HTML documents have a more relaxed structure. It allows for certain elements to be optional, and it is forgiving of errors in document structure.
XHTML: XHTML documents must adhere to a stricter structure. Elements must be properly nested, and the document must have a well-formed XML structure. Any deviation can result in parsing errors.
Self-Closing Tags:
HTML: In HTML, self-closing tags for void elements (e.g., <img>, <br>, <hr>) are optional, and some developers choose to omit the closing slash (/>).
XHTML: XHTML requires self-closing tags for void elements to have a closing slash (/>). Omitting the slash may result in parsing errors.
Attribute Quoting:
HTML: In HTML, attribute values can be specified without quotes, as long as the values do not contain spaces or certain special characters.
XHTML: XHTML requires attribute values to be enclosed in double or single quotes. This is a stricter rule to ensure consistency and compatibility with XML.
Error Handling:
HTML: HTML browsers are designed to be forgiving of errors. Even if there are mistakes in the markup, browsers often try to render the content as best as they can.
XHTML: XHTML is less forgiving of errors. If there are syntax errors or violations of XML rules, XHTML documents may not be rendered correctly. This makes it important to write well-formed XHTML documents.
In summary, while HTML and XHTML share many similarities, XHTML is a more strict and XML-compliant version of HTML. The differences lie in syntax rules, document structure, handling of self-closing tags, attribute quoting, and error handling. As of my last knowledge update in January 2022, HTMLWhat is the has become the dominant standard, and many of the differences between HTML and XHTML have become less significant in modern web development.