URLfragment

URLFragment, commonly called a fragment identifier, is the portion of a URL that follows the hash character (#). It designates a particular location within the primary resource, such as a section in a document or a named anchor. The fragment is intended for client-side use and is not typically sent to the server as part of an HTTP request.

Syntax and placement follow the general URL structure: scheme://host/path?query#fragment. The fragment value is the part after the #, and it is usually percent-encoded to ensure safe transmission. In practice, browsers interpret the fragment by locating an element with an id matching the fragment value and scrolling to it if present. If no matching element exists, the browser may not change the view.

JavaScript and web APIs expose the fragment through properties such as window.location.hash, which includes the leading #. The substring after the hash can be read and changed programmatically, triggering events like onhashchange when the fragment changes. This enables dynamic in-page navigation and client-side routing in single-page applications.

Common uses include linking directly to sections within long documents via anchor tags, styling the target with CSS using the :target pseudo-class, and implementing hash-based routing in SPAs. Historically, some sites used hashbang (#!) for AJAX-driven content, though modern applications often rely on the History API for cleaner URLs.

Overall, the URL fragment provides a client-controlled navigation aid that does not affect server requests, supporting accessible anchors, in-page navigation, and client-side routing strategies.