Canonical tool. Use the canonical tool to check if a page has a canonical tag and to find out which page should be index by search engines based on the canonical location. The syntax used for a canonical tag: HTML Mark-up = <link rel=”canonical” href=”http://example.com/page.html”/> HTTP header = Link: <http://www.seoreviewtools.com/canonical-url-location-checker/>; rel=”canonical” The canonical tag is supported by:Google, Yahoo, .....