XHTML (eXtensible HyperText Markup Language) is a markup language that is a reformulation of HTML 4 as an XML application. It is designed to be stricter and cleaner than traditional HTML, adhering to the stricter syntax rules of XML. This means that all tags must be properly nested, all tags must be closed, and attribute values must always be quoted. The primary goal of XHTML was to bridge the gap between the flexibility of HTML and the strict structure of XML, making web content easier to process by machines and more accessible. It was intended to be the successor to HTML 4.01, offering better integration with other XML-based technologies. While modern web development has largely shifted towards HTML5, XHTML remains relevant in specific contexts, particularly where strict XML compliance is required, such as in mobile device rendering or specific application environments. It combines the presentation capabilities of HTML with the structural rigor of XML.