What is Canonical URL

Canonical URL defined as the preferred URL for the page content to be indexed in the Major Search Engines. Canonical URL is used by the Major Search Engines like Google, Yahoo, Bing, etc. Many websites have two or more links of the same content with different parameter. In this time Search Engines are confused about Which One is needed to be Index?

Canonical URL Example

Example if I am taking this same page URL
ORIGINAL URL: http://www.bestseoideas.com/url-optimization/what-is-canonical-url
I want to pass the referral Parameters so the Original Link will be changed like below
URL with Parameters: http://www.bestseoideas.com/url-optimization/what-is-canonical-url?utm_source=bestseoideas&utm_medium=referral
The above Example URLs that are not same but the content showed in the page is exactly same content. Search Engine confused which one need to be indexed. To resolve this issue Canonical URL will be used in each and every page.
Canonical URL: http://www.bestseoideas.com/url-optimization/what-is-canonical-url
So the above URL only will get indexed by major search Engines and redirect all the users to this URL by using the Canonical tag. While the rel="canonical" link element is seen as a hint by Search Engines and not an absolute directive.

Applying Canonical URL to a normal and non Canonical URL

We need to add a rel="canonical" link to the section of the non-canonical version of each HTML page. Below is the Canonical URL tag of the current page, <link rel="canonical" href="http://www.bestseoideas.com/url-optimization/what-is-canonical-url" />
We need to place the above code in the head section of the HTML code then the page content is placed in canonicalize url.