What is Canonical Tag?

Canonical tagging is nothing but adding a HTML element is to the section of an html page. This helps Google to identify duplicate content by specifying word "Canonical", Google will identify what is preferred version (URL) of the page. It is supported by Yahoo & Bing as-well

For Google, showing relevant pages is most important and one of the key challenges for Google is to avoid displaying duplicate pages in search results in Analytics. Canonical tagging helps Google identify duplicate pages and show only relevant pages. The basic purpose of canonical tagging is simply to keep duplicate content out of the search engine index while consolidating preferred page’s strength.

Before we go deeper, one needs to know the conditions in which the duplicity of content arises.

On Internet, duplicate content issues can occur in the following conditions.

1) Same content is accessible from various URLs

Eg: www.worldwebsolutions.in

And www.worldwebsolutions.in/index.html

can be considered as different page by search engines even though they represent same content and page.

2) Another classic example is there are different URL for same¬ page but content is displayed in table format with results are sorted differently.

3) When a site is configured to display results on https, http or non www version. i.e.www.worldwebsolutions.in or http://www.worldwebsolutions.in or https://worldwebsolutions.in Search Engines consider above three different URL as different URLs although all have same content in it.

4) Content that one might have created for a blog is syndicated across other sites or replicated in full or in parts.

So how this is implemented?

Let’s take real case example on Flipkart.com

Generally in Ecommerce sites, single product page might dynamic URLs based on user session, search preferences, sorting etc.

E.g.: All the following pages show Moto E product primarily on Flipkart have different URLs

• http://www.flipkart.com/mobiles-accessories/pr?p%5B%5D=sort%3Drelevance&sid=tyy&filterNone=true&q=moto

• http://www.flipkart.com/mobiles-accessories/pr?p%5B%5D=sort%3Dpopularity&sid=tyy&filterNone=true&q=moto

• http://www.flipkart.com/moto-e-1st-gen/p/itme7zd2zsjgbhxg?pid=MOBDVHC6XKKPZ3GZ

• http://www.flipkart.com/moto-e-1st-gen/p/itme7zd2zsjgbhxg

But all these page point to single product i.e. Moto E.

It is important for Google & Flipkart to identify that all these pages belong to same product / service and it is up to webmasters to help Google to identify of all these page which is the preferred page. This preferred page would be displayed in the search page.

Here http://www.flipkart.com/moto-e-1st-gen/p/itme7zd2zsjgbhxgURL is the preferred page and so in all above mentioned pages the following html tag is added

With this Google identifies and gives preference search result to above page. See below image for reference.

reference.

One see the source code of moto – e product, all pages have same Canonical Tag

See below image for reference.

Advantages of Canonical Tags

1. Using canonical tags helps Google to link duplicate and similar content pages together so that Google can consolidate information under various pages under single preferred page.

2. Canonical tags also help us getting better tracking metrics, as it is difficult to track multiple URL’s for same piece of content.

3. Canonical tags helps in determining the URL which users wants to see.

Eg: users generally prefer URL’s which is easy to understand

4. Canonical tags helps in addressing content syndication of URL which are published on various domain to preferred URL