Which technology is primarily responsible for structuring web content?

HTML, or HyperText Markup Language, is the foundational technology used for structuring content on the web. It provides the basic framework of a webpage, allowing developers to define elements such as headings, paragraphs, images, links, lists, and other types of content. HTML tags are used to encapsulate the various pieces of content so that browsers can correctly interpret and display them to users.

For instance, using tags like <h1> for main headings or <p> for paragraphs helps convey the organization of the content. This structural capability is essential for ensuring that web content is not only displayed accurately but also accessible, as it allows screen readers and other assistive technologies to interpret the content effectively.

In contrast, CSS (Cascading Style Sheets) is used for styling and layout but does not structure content. JavaScript adds interactivity and dynamic behavior to the web pages but does not provide a structural backbone. XML (eXtensible Markup Language) is a markup language that can structure data for various purposes but is not primarily used for web page content structuring like HTML. Thus, HTML is the correct answer as it is specifically designed for organizing and structuring web content.