URL Canonicalization & Rel=Canonical Tag – Best Practices for SEO

Five years ago, Google introduced rel=canonical tag, a single one line HTML code but very powerful. Most of the webmasters are confused and still not aware of the use of rel canonical tag its advantages properly.

I was reading some article and I found out a few very interesting things about rel canonical tag, so here I am sharing how to use and take the best out from this tag.

What is Canonicalization?

Canonicalization is a very interesting and important concept and essential to creating an SEO optimized website. The main problem Canonicalization fix is the duplicate content issue.

rel canonical tags for SEO

Image Source – Moz.com

Sometimes, there are multiple copies of a single content present on the website pages or on multiple sites, to provide the best user experience, search engines have to choose any one dominant version of the page which is most likely to be the original or the best one.

Here comes the role of rel=canonical tag. Through URL Canonicalization using rel canonical tag, an individual web page can be accessed from multiple URLs without any content duplication issue. There will be only one best URL (the one declared in the rel=canonical tag) for Google to consider.

URL Canonicalization for SEO

When there are multiple URLs for a single web page, the popularity or you can say the authority of the page splits up. To keep the page authority to a single web page only, URL canonicalization is essential.

This happens mostly with web developers. To resolve this, Google recommends using rel canonical tag for the canonicalization of the URLs. Check Matt Cutts giving SEO advice on URL canonicalization in his blog post.

What is Rel Canonical tag?

Rel canonical tag is a HTML tag used on a web page to indicate Google about the original master copy of a web page. It is basically used to tell Google about the preferred URL that should be considered for a page when there are multiple URLs are present for a single page.

The rel canonical URL tag tell search engines that certain similar URLs are actually the same. It allows you to have a single web page to be accessible under multiple URLs, even on multiple websites without creating any duplicate content issue or harming your rankings.

Google is very strict on the duplicate content issue, so when there are multiple versions of a page created by itself or by users then there are possibilities that Google may index the duplicate pages and rank them higher as compared to the original page.


Take your page rankings down over the duplicate content issue. You may become the victim of panda penalties due to this duplicate content.

rel=canonical URL tag sample

link rel=”canonical” href=”http://example.com/give-me-some-example” /

All you need to do is place this above code in the source code of the web page.

The Process of URL Canonicalization

Canonicalization is the process of picking up any one best URL. In some cases, you will get the best URL easily, whereas, in other cases, you might face some confusions.

Be calm and pick any one URL when you are confused with choosing the best one from a bunch of URLs. Not canonicalizing your URls is always worse than canonicalizing your website URLs.

Where Can you use Rel Canonical tags?

  • On duplicate URLs with tracking codes
  • On duplicate URLs with session ids
  • Landing pages on your website
  • In case you are not sufficient enough to implement a server side or a 301 redirection
  • Syndicating your content while content marketing activity (Cross-domain)
  • You can use rel=canonical tag on pages with duplicate content or near duplicate content

Note: Here near duplicate means pages like eCommerce website where for a specific product everything is same but the only difference is the color variants.

Or on the different homepage versions of a website.

  • www.example.com
  • example.com/
  • example.com/home.asp
  • www.example.com/index.html

So far, webmasters are using rel canonical URL tag to remove duplication on the website internally and helping Google in canonicalization process to pick the best URL to show in search results.

Many webmasters have this confusion that rel=canonical 301 re-directions are the same and you can use anyone of them, but it’s not like that.

Example of using rel=canonical URL tag

Let me explain this with an example: There are a few

There are a few URLs for a single page

PageA – www.example.com/accessories/nivia-comb

PageB – www.example.com/accessories/nivia-comb/colorid=2

PageC – www.example.com/accessories/nivia-comb/colorid=3

PageD – www.example.com/accessories/nivia-comb/sessionid=19090

Here comes the issue of duplicate content.

To resolve this issue and to tell Google that PageA is the original version and Page B, C D are the duplicate URLs of PageA, use Rel=Canonical tag on these pages.

Place link rel=”canonical” href=”www.example.com/accessories/nivia-comb” / in the head/head section of the page source code.

It will indicate Google that the original page is the PageA and others are just the duplicate ones. So that original preferred copy of PageA will be cached and indexed by search engine and it will rank in search results.

All the SEO values will also be passed to the PageA URL i.e. Google will not cache or index PageB, C D URLs, and they will not appear in search results

and if any link is pointing out to the Page B, C or D URL then the value of that link will be passed to PageA URL.

JCPenney Example:

Here are the two URLs of a product page at JCPenney store

Url1 – http://www.jcpenney.com/gifts/for-him/the-foundry-supply-co-performance-pocket-tee-big-tall/prod.jump?ppId=pp5002260206catId=cat1002310004subcatId=cat100250139deptId=dept20000014colorizedImg=DP0318201419090047C.tif

Url2 – http://www.jcpenney.com/gifts/for-him/the-foundry-supply-co-performance-pocket-tee-big-tall/prod.jump?ppId=pp5002260206

If you check both the URLs in the browser, then you will see that both URLs are pointing out to one single page, the only difference here is the URLs used by the users to reach to that page.


In the URL1, multiple tracking ids are being added to the end of the URL making it very long. This URL will be cached indexed by Search engine.

Now if any user link to that URL or share it on social media then its value will increase in terms of SEO and it will start ranking higher as compared to URL2.

Solution to the Issue:

Include rel=canonical tag in the page source code, so that whenever there is a duplicate version get created, It will be handled by this tag.

If you see the page source code URl1, canonical tag for the preferred page is already present there.

link rel=”canonical” href=”http://www.jcpenney.com/gifts/for-him/the-foundry-supply-co-performance-pocket-tee-big-tall/prod.jump?ppId=pp5002260206?/link canonical tag present on the JCPenney page

canonical tag for preferred page present

This canonical tag pointing out to the original copy of the page is telling Google that this (the above link in the image) is the original version and others are just the duplicate ones. So cache, index, and rank this version of URL only.

Note: Here one thing to keep in mind that “there is only one page with multiple generated URLs. So when it comes to placing a canonical tag, It is always placed in the head/head of the original page source code.

Difference Between Rel=Canonical Tag 301 Redirections

This is a very important thing to know. Rel canonical tag 301 redirections are similar from the SEO point of view but both of these techniques are not interchangeable.

Rel canonical tag is a page level tag and needs to be implemented on each page while 301 redirects are implemented on URL level.


Task – Redirect Visitors from Page A——- Page B OR use rel canonical tag

Difference 1:

If you apply a 301 redirection on Page A to Page B then it redirects all the visitors from Page A to Page B. In this case visitors will not be able to see the Page A anymore.

While in rel canonical tag, It does not redirect the visitor from Page A to Page B. It just tells Google that the original version is actually Page B, so Google should cache index Page B and show it in search results rather than Page A.

Difference 2:

In 301 re-direction you cannot see the page even if you have the exact old URL of the page. When crawler comes to the old page it is redirected to the new page.

In rel=canonical tag, you can see the old page using its exact old URL. When crawler comes to the old page, It is notified about the preferred version and redirected to it.

Understand Rel Canonical tag 301 Redirections

Which one should I Use? Rel canonical tag or 301 redirections

If you want to consolidate new and old version of pages permanently and remove duplicates then you should use 301 re-directions, But, If you want to keep both the copies of a page live for your users and want to show only 1 version in search results then you should use rel canonical tag.

If you are going for a permanent redirection from the old website to the new website then you should go for 301 redirections or a server-side redirection, But if all these options are not possible then you should go for the rel=canonical tag option. (Make sure both the copies of web pages are same or nearly same).

301 redirection gives a clear signal to the crawler and users that which URL should be indexed and it is widely supported by all the search engines, While rel canonical tag is just a hint for search engines.

Does rel=canonical Pass Page Authority Link Juice?

Just like a 301 redirection, rel=canonical also passes authority and page rank if used properly.

Will Google cache or index those duplicate pages? NO

If you apply rel canonical tag on a page then Google neither cache nor index any copy of the duplicate pages, they also do not appear in search results. Only the original version of the web page is cached, indexed and rank in search results.

Here take a look at a practical test done by @tonyadam on his own website.

Other Uses of Rel Canonical

Use Canonical URLs Cross-domain for Content Syndication

Have you seen content from one website is published on another website without affecting the rankings or creating any duplicate content issues for the original publisher of the content?

This is possible through cross domain canonical URLs. Now create content and publish it on your website as well as other popular websites without any harm. Get eyes for your content and links as well.

Use Rel=canonical in combination with hreflang

if you have your website in multiple languages, make sure you use hreflang. Each language’s canonical should point to itself. Check this guide from yoast for better understanding.

Self-referencing Canonical URL on all Website Pages

This is the solution of all the problems. Adding a canonical URL tag on every page of the website will lessen the possibilities of content duplication because no matter how many URLs get created for any of the website pages, the best one, the canonical URL has already been declared during the time of the creation of the page.

Points to Remember while Implementing Canonical URLs

1. When canonicalizing paginated archive, do not canonicalize archive to page 1. The rel=canonical on page 2 should point to page 2 only. If you point it to page 1 only then search engines will not index links on deeper archive pages such page archive 2,3,4 etc.

2. Do not use multiple rel=canonical links on a single page.

3. Always use one single version of URL across the website.

4. Use rel=canonical tags on similar pages only

5. Rel=Canonical is a page level tagging and should be implemented on each page of a website. Implementing only at the home page for the whole website doesn’t work here.

6. For moving from old site to new site, Always prefer 301 redirections, because canonical tag is just a hint for Google and other search engines treats it differently

7. Do not use no index robots meta tags or block the page with robots.txt where rel=canonical is implemented otherwise search engine will not be able to crawl or read your canonical tag on that page.

Still have questions in your mind? Check this article by Dr. peter on rel=canonical tag FAQs. Rel canonical URL tag is very powerful and it can boost your website SEO by if you use it properly on your website.

Please comment below if you have any suggestions or queries related to this post.

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