windowlocationhash

Windowlocationhash refers to the fragment portion of the current document URL, accessible in JavaScript as window.location.hash. The fragment, known as the hash, starts with a leading # and is used for in-page anchors or as a client-side routing mechanism in single-page applications. The value of location.hash includes the leading #, for example #section.

Reading and writing are straightforward. To read the current hash, access window.location.hash. To set it, assign a string that includes the leading #, such as window.location.hash = '#section'; you can also assign without the leading # in many browsers, which will be normalized to include one. Clearing the hash results in an empty string.

Changing the hash does not cause a full page reload in most cases. Instead, browsers typically scroll to an element whose id matches the hash (if such an element exists) and push a new entry onto the session history. If you want to replace the current history entry without adding a new one, you can use the History API or location.replace.

Events are used to react to hash changes. The hashchange event fires on the window object whenever the hash portion changes, including when the page is loaded with a non-empty hash. The event provides access to the oldURL and newURL, enabling state synchronization or UI updates in response to navigation.

Common uses include in-page navigation to specific sections, maintaining UI state in single-page applications, and enabling deep linking. Because the hash is not sent to the server with HTTP requests, it is a client-side mechanism and should not be relied on for secure state or server-side access control. It is often used in conjunction with the History API (pushState) for more flexible URL management.