How to use canonical tags to take care of duplicate content: E-Commerce site

Imagine how frustrating it will be if a SERP contains 10 URLs from the same website with the same content. It will be extremely tough to find quality content from different websites. This would probably be one of the best black hat SEO techniques (if it works out). Luckily enough for us, Google penalizes duplicate content and there is a tag which, if used, will help you in saving your website from getting penalized. It is the rel canonical tag.

According to Google, The rel=”canonical” link consolidates indexing properties from the duplicates, like their inbound links, as well as specifies which URL you’d like displayed in search results.
The rel=canonical tag tells the search engines about which URL does the site wants to list on the SERPs. If not used, it’ll create a clutter of useless pages (which are the same pages) and the SEO juice will be divided unnecessarily between those pages.

There are different URLs that a particular page might have. You need to check them and add the canonical tag.

http://www.360digiworld.com/bananas (Main URL)
http://www.360digiworld.com/bananas.html
http://www.360digiworld.com/bananas?utm_campaign=gru
http://www.360digiworld.com/bananas#more
http://360digiworld.com/bananas
http://360digiworld.com/bananas.html
http://360digiworld.com/bananas?utm_campaign=gru

These are all URLs of the same page but they come out as different pages if the canonical tag is not used. The www and non www issue can be resolved using 301 redirects but you will have to use the canonical tag for the rest of them.

Flipkart’s case with canonical tags:

With e-commerce sites, the problem is having the same product in different color, size, memory(in case of laptops, phones etc. ). I will take the case of a product with different colors.
Nokia Lumia 520 comes in 5 different colors – Red, Yellow, White, Black and Cyan.
When I searched “nokia lumia 520 flipkart” on Google, this is how the result page looked:
google search for finding the canonical tags
The URL of the first result is http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj and it takes me to the Nokia Lumia 520(Red)’s page.
how flipkart uses canonical tags
Next, I searched for Nokia Lumia 520 on their site which listed all the 5 colors. Following were the URLs of the pages:
Yellow: http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj?pid=MOBDJ4ZNPKRUWTV9
White: http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj?pid=MOBDJ4ZNC7PTMG68
Black: http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj?pid=MOBDJ4ZNAPHAUMSH
Cyan: http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj?pid=MOBDJ4ZNKFFGYJC4
Red: http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj?pid=MOBDJ4ZNY4G5TJEC
Note: I have removed the search parameters from the URLs for simplifying the URLs.
When I checked the source code for all these pages, the common code was
link rel="canonical" href="http://www.flipkart.com/nokia-lumia-520/p/itmeyfpbsg7tajzj"/

how to check canonical tag in source codeWhat this tells the search engines is that no matter what color people are searching for Nokia Lumia 520, show the page with Red Nokia Lumia 520! It may kill the user experience, but it’s better to have visitors coming to your site and finding the color they want instead of getting penalized and having no visitors at all.
To confirm the case, I searched “nokia lumia 520 white flipkart” on Google:
proof for canonical tagsVoila! The URL is still of the Nokia Lumia 520 red’s page.

This confirms the fact that the Red Nokia Lumia 520’s page has been defined as the parent page of all other Lumia 520’s pages.
So now that you know how Flipkart uses the rel=canonical tag to list its pages, you should start implementing the same on your website. But before that, here are the errors to avoid when using the canonical tag:

1) You can use both absolute and relative URLs but use them in the correct way.
common errors while creating rel canonical tags2) The rel=canonical tag should only appear in the of the code. If declared more than once, Google might just ignore all the declarations.
3) Don’t send mixed signals. If you have 3 pages, say
a) http://www.360digiworld.com/bananas/dave
b) http://www.360digiworld.com/bananas/stuart
c) http://www.360digiworld.com/bananas/hulk
Now if page “a” has been canonicalized to page “b” and page “b” has been canonicalized to page “c”, it becomes complex for unnecessary reason. This is known as Daisy Chaining. Moreover, if you think something like this is going to happen, you should point the URLs to one single URL instead of creating a chain. Daisy chaining just confuses the crawlers.
You must also check if the page that you have canonicalized to – exists. In this case, hulk does not belong to team minions. Hence, it will give a 404 error. You will lose the value for all the pages.
These were few mistakes you should avoid while using the canonical tag. Feel free to share your thoughts in the comments section below.

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