How does the Canonical Link Element work?
The canonical link element (tag) works by using a small piece of HTML code to tell search engines that a webpage is a duplicate of another webpage. It is important when using multiple website versions including https, www and non-www and separate dedicated mobile sites for example. It also helps to fix and avoid duplicate content. The canonical link can play a pretty big role in SEO today and it also passes on link juice from the webpages that are canonicalised.
How to apply the canonical link element
Canonical Code Example–
<link rel=”canonical” href=“http://example.com/pageone/” />
By adding the example code to the head of the html on the page http://www.example.com/pagetwo you are specifying to search engines that page two is canonically linked to the page one.
When to apply canonical link?
The two main reasons to canonicalise your website or pages are when you have multiple URL’s that lead to the same destination or when you have similar webpages that could been seen by search engines as duplicate content.
Both these addresses will end up on the same destination webpage thanks to 301 redirects. This may not seem important but the different https and http versions can affect SEO. Let’s say someone links to the http version and someone else links to the https version. That means that http version got one vote of confidence and the https one vote of confidence. What we really want is two votes of confidence passing link authority to the one preferred version. This is where the canonical link tag comes into action. By using a canonical link you are basically telling search engines that this is the preferred version of my website or page. In this way link authority will consolidate and strengthen the page rank for the preferred version. Otherwise you can risk diluting the link authority amongst the different versions of a website or page.
Another important time to use a canonical link relates to duplicate content. Let’s say a website is selling five products that are basically the same beside a few small differences. Google might consider these kind of pages duplicate content and possibly even remove some of them from their index. By using the canonical link element you can specify that these webpages are related. It makes sense to have all the link authority pointing to one preferred product. This way when the individual products are linked to, it will strengthen the position for the product that is shown in the search results.