XHTML (Extensible Hypertext Markup Language) is a markup language that is a stricter and cleaner version of HTML. It is designed to be a more robust and standardized way to create web pages. Unlike HTML, XHTML documents must be well-formed, meaning they adhere to strict XML syntax rules. This includes proper nesting of elements, closing all tags, and using lowercase for all tag names. XHTML was intended to replace HTML, offering better compatibility with different browsers and devices. It enforces a more structured approach to web development, making it easier to parse and process by machines. While XHTML was initially seen as the future of web development, HTML5 has since become the dominant standard. However, XHTML is still used in some contexts, particularly where strict XML compliance is required or preferred. XHTML documents are typically served with a MIME type of application/xhtml+xml, which tells the browser to parse the document as XML.