Using Canonical URLs

You might have heard about canonical URL’s but not sure what is it? And how to use it?

Relax, this article will lay a clear foundation about Canonical URLs

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

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.
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.

Example: Say blog.edupristine.com/first-post.html is also syndicated at its sister site www.edpri.com/blog/first-post.html though the content is same, search engine might consider as completely different URLs.

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.

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.

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

In Addition to example shown with Flipkart case study, one can/must do the following action to improve search visibility as suggested by Google

1. Setting your preferred domain in webmasters section

In Google webmasters for a website, one can set their preferred setup
i.e, once these sets are done, Google will prefer selected version for search results

2. Using preferred URL html tag with rel=”canonical” HTML link element

See as mentioned above in the flipkart Moto E example

3. Use 301 redirects for URLs

Eg; In page such as

One can choose one page as canonical and rest can be redirected to that selected canonical page URL.

4. As mentioned by Google itself, for canonical links Google Prefer HTTPS over HTTP except when there are conflicting signals such as the following:

• The HTTPS page has an invalid SSL certificate /contains insecure dependencies

• The HTTPS page is roboted (and the HTTP page is not).

• The HTTPS page redirects users to or through an HTTP page.

• The HTTPS page has a rel=”canonical” link to the HTTP page.

• The HTTPS page contains a noindex robots meta tag

One can ensure this behavior by taking any of the following actions:

o Add 301 or 302 redirects from the HTTP page to the HTTPS page.

o Add a rel=”canonical” link from the HTTP page to the HTTPS page.

5. Managing Dynamic parameter in URL’s

One can inform Google to ignore certain parameters in an URL

i.e. price range (“From to To” in the URL string or session id in a URL)

6. Using canonical link in the http header for Non HTML pages (PDF etc)

One configure in the webserver where by using rel=”canonical” in the http header to

Indicate canonical URL for HTML documents, PDF’s etc.

In this case, one can use a rel=”canonical” HTTP header to specify to Google the canonical URL for the PDF file, as follows:

rel=”canonical”

Canonical Tagging is very important for SEO as it directly helps google in its search algorithm so Canonical tagging has high significance in Google Algorithms.

Canonical URLs are extremely important for E-commerce companies, Content heavy sites and sites where there is significant search traffic

Hope this articles answers all your queries. If not please leave a comment and I shall try my best to clear all your doubts.