Breadcrumbs are optional and are disabled by default. See the topic Adding breadcrumbs to an HTML output for information on how to control whether breadcrumbs appear or not.

Each breadcrumb links to its respective topic. If the path to the topic includes topicheads, those will not be links because a topichead can’t be a link target.

If a topic appears more than once in a publication, you must populate the copy-to attribute of the additional instances of the topic to specify a unique output filename. You set the copy-to attribute on the topicrefs of the additional topic instances. If you do not set the copy-to attribute, the breadcrumbs for the topic will include multiple paths for every instance.