Canonicalization (On Page Optimization of Duplicate Contents)
Canonicalization is a process of picking the best URL when there are several choices.Canonical attributes are used in link tag to tell search engines that the content is duplicate and is not required to be indexed. If you are wondering how this will be helpful then the problem which I faced few years ago can explain things in a better way.
Three years back I was doing SEO for a Web Directory i.e website that accepts submissions of website links in various categories. In every category there was a hyper-link to submit page with the category id as a get parameter, Resulting in various hyper-link to submit page, there were more then 100 categories resulting in more then 100 hyper-links and each of that hyper-link was indexed in Google search engine result page. Links were quite similar to
Google index them individually however the content of all these links were similar. In Google’s database there were more then 100 pages with almost duplicate content and website was suffering in SEO because of this duplicate content getting indexed. At that time search engines were not supporting Canonical attribute, So I had to change the code of that website and had to compromise with the functionality of that website to optimize that website for SEO.
Things have changed, Year back Yahoo, Bing, Google have announced that they will be supporting “canonical url tag” to help web-masters and site owners eliminate self-created duplicate content.
In-case you are facing similar problem as mine or you are facing any other similar problem of duplicate content of your site getting indexed in search engines then you don’t to have to change the functionality of the site, like I did.
You can simply use canonicalization and things will resolve for you. Now let us see the usage of canonical attribute. It has to be used like
Here canonical URL refers to the URL that is the original of duplicate content.
For example, In my scenario All I have to do is to put this canonical tag
in this page
now every page like
Will be sharing that canonical tag and will avoid the duplicate content to be indexed in search engines.
You have to use this link tag between the head tags of your page.
There are few points that Google has said in their official blog, I am listing them
1) Canonical is a hint that search Google strongly honor.
2) Canonical Links can be absolute as well as relative paths.
3) If pages are slightly different, still Canonical can be used.
4) In case your canonical link gives a 404 error then Google will use their heuristics to find the canonical.
5) Redirect links can be used a canonical.
6) If canonical link has not been indexed then the canonical link will be reconsidered after canonical link gets indexed.
In past Google was only accepting canonical link of the same domain or the sub-domains of same domain but recently Google has made the announcement that Google has started accepting canonical links of cross domains.
If you are facing problem of duplicate content getting indexed then I am sure that canonicalization can resolve your problem.