n. A tag used to ensure search engines are looking at the true version of a page. For example, if there was a page that was duplicated across multiple websites, in order not to be dinged on other websites for duplication of content, a rel=canonical would be put on every page except the original. If a website has a lot of duplicate content (i.e. search pages, directories, etc.) a rel=canonical should be used so that each page is not crawled individually.