Fragmentids

Fragmentids, or fragment identifiers, refer to identifiers used to reference a specific portion of a resource. They are most commonly seen as the part of a URL following a hash (#) symbol and can serve as in-page anchors, bookmarks, or routing cues in web applications. In other contexts, the term fragment ID is also used to describe an identifier for a fragment component in user interface frameworks.

In web URLs, the fragment is the string after the #. It is not transmitted to the server in HTTP requests; the browser uses it locally to locate the element with an id attribute matching the fragment, or to trigger client-side navigation in single-page applications through hash-based routing and hashchange events. For example, https://example.org/docs#installation refers to the element with id="installation" on that page. If no matching element exists, most browsers leave the page view unchanged. Fragmentids enable lightweight, linkable navigation within a document without requiring server-side state.

Fragment identifiers are defined in URL syntax by standards such as RFC 3986. They are typically percent-encoded to preserve special characters. Because the fragment is not sent to the server, it should not be used for authentication or any state that must be verified server-side; it is primarily a client-side navigation and bookmarking mechanism. In practice, fragmentids are also used in single-page applications to reflect navigational state, and in documentation or markup to reference a named portion of a document or resource.

Outside the web, fragment IDs appear in other domains as well. For example, in Android and other UI frameworks, a fragment ID identifies a specific fragment component in a layout or during runtime management, while in markup and semantic contexts, a fragment after a hash may point to a sub-resource within a document.