Inspect the Canonical URL of a website
The canonical url in the HTML head is a mechanism to tell search engines which page is the one with the original information. When you have a page with pagination, you always want to index just the first page. Just add a canonical url to the others and search engines will just index the first page.
This plugin is to inspect the usage of canonical urls on websites. Just visit the page and you will see a little canonical icon.
There are three states of the canonical url:
1.) no icon: The current website has no canonical url specified.
2.) grey icon: The website urls matches the canonical url.
3.) blue icon: The canonical url for this site is another url. Click on the icon to go to the specified canonical url.