URL fragments: Anchors defined with the `id` (and formerly `name`) attribute in HTML, visible via `location.hash` in JavaScript. This is possible to do right now via executing code in JavaScriptCore on page loads but it would probably be more efficient* to have a proper API endpoint to list the available fragments. A use case for this would be to list fragments either in a menu or when completing the URL. *: document.anchors seems to be only for the `name` attribute and I haven't found a better solution than going through each node and checking if they have an `id` attribute