Is Poor Canonicalization Killing Your SEO? Easy Ways to Create Canonical URLs

First off, let me explain what canonicalization is. According to Matt Cutts:


"Canonicalization is the process of picking the best url when there are several choices, and it usually refers to home pages."

What are these "several choices"? Sometimes Google has more than one version of one and the same page indexed:

www.example.com

example.com

www.example.com/

example.com/

www.example.com/index.html

www.example.com/?icf=blahblahblah

etc.

Google treats them as separate URLs, but intelligently assumes that they lead to one and the same webpage. In which case it normally picks and returns just one URL out of the group in the search results.

Why is this preferred URL called "canonical"? Well, Google calls such URLs "canonical" - Bing calls them "normalized". In a word, for some reason they appear the most standardized and uniform to search engines.

And now, the ultimate question - why would you worry about it anyway? And here is why: poor canonicalization may have quite a detrimental effect on your site's rankings. And vice versa, by telling search engines "Hey, here is my canonical, my preferred URL", you can substantially improve your site’s positions in the SERPs.

How does this work? Imagine, that

example.com has 1250 backlinks, 12454 Alexa Rank, PR 3

www.example.com has 15000 backlinks, 12354 Alexa Rank, and PR 4

and

www.example.com/ has 350 backlinks pointing to it, 23985 Alexa Rank and PR 2.

If none of these URLs is specified as canonical, the SEO value of your homepage may get split between the three variants. No need to say that this will have a negative effect on your site's rankings.

Let us consider another example. The two URLs on the Saks Fifth Avenue site look slightly different but return identical content:

http://www.saksfifthavenue.com/main/ProductArray.jsp?N=306418048+399545540+4294912360

http://www.saksfifthavenue.com/main/ProductArray.jsp?Ns=P_saleprice&N=306418048+399545540+4294912360

This is because there is more than one way to access the same content on this site (which is typical of most e-commerce websites). You can browse by price, color, designer, etc.

Just like users can go 100s of different paths, so can search engine bots. This may lead to the duplicate content issue within one site (URLs with duplicate content indexed) and, again, the distribution of PageRank between multiple webpages. However, these issues can be easily dealt with by specifying your canonical URLs.

So, if you want to get the most out of your SEO efforts, having control over your webpages' canonicalization is key.

Ways to Specify Canonical URLs

What signals does Google use while picking a canonical URL out of a group of similar-looking ones? Well, it uses quite a complex algo for that, but there are certain ways for SEOs to mark their canonical URLs, so that Google picks the ones with the most SEO value to show in the search results:

1. Link internally to your canonical URLs

If Google sees that your WWW page has internal links pointing to it and your non-WWW page has none, it will probably decide that your WWW page has more authority than your non-WWW page. Thus, pick only one exact variant of your webpage, for instance www.homepage.com/ (slashes and other symbols also make a difference) and link to it consistently.

2. Specify your preferred URL in Google Webmaster Tools

You can also specify whether they would like Google to give priority to your WWW or non-WWW URL in Google Webmaster Tools, and Google will respect that. To set your preferred URL, go to Site configuration > Settings > Preferred domain in your GWT account.

3. Edit your .htaccess file

You can also specify whether you want your site to be WWW or non-WWW in the .htaccess file of your root folder.

RewriteEngine On
RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

4. Make all your backlinks go to your preferred URL

It is hard to control how others link to your site, but, whenever you can, make sure all your backlinks lead to one single variant of your URL.

5. Use 301 redirects

This is a common practice for many SEOs. Using a permanent 301 redirect makes all the link value from the original page flow to the destination page, so, it's quite a good way to deal with the canonicalization issue. However, for various reasons, such redirects are not always possible.

6. Use a CMS that supports standardized URL

Some content management systems (CMS) take care of the duplicate URL issue themselves, by making all URLs uniform.

7. Include your preferred URLs in your sitemap

Search engines also look at your sitemap while deciding which URL to pick as your canonical one. So, make sure that your sitemap contains corresponding variants of your URLs.

8. Tell Google what parameters should be ignored

What about different php parameters that you need for analytics? You can go to the URL Parameters section in Google Webmaster Tools and tell Google to ignore those parameters in your URLs. If you do that, Google will consider

www. example.com/

and

www. example.com/?icf=blahblahblah

one and the same URL.

9. Use a "canonical" tag

The canonical tag (scientifically called "parameter") was introduced by Google in 2009. Other search engine giants - Yahoo! and Bing - agreed to support it as well. It made big news and meant a lot to SEOs back then - SEs finally had given webmasters an effective lever to control canonicalization. By adding a canonical tag to your URL, you sort of put a sticker that says "Canonical" on it. However, search engines reserve the right to ignore it, so, the canonical tag is not a universal solution to all canonicalization-related issues.

Here is how it can be added to your URL:

http://www.example.com/index.html

in the head part, you specify:

<head> …

<link rel="canonical" href="http://www.example.com"/>

Mind the slash right after "http://www.example.com".

Now, one important thing to remember. If there is a way to point out your canonical URL that doesn't involve applying the canonical tag - go for it. It's always better to specify your preferences at an earlier stage. The use of the canonical tag is only justified when there is no other way to point to your canonical URL. For example, sometimes you can't use a 301 redirect because you have a free-hosted site, etc.

Also, avoid creating chains of canonical tags, that is, one URL being canonical to another URL, while it itself has a canonical URL for it. That might confuse Google and lead to Google ignoring your canonicalization instructions. Besides, make sure to avoid infinite loops, that is URL A being canonical to URL B, while URL B is the canonical one for URL A.

What the Canonical Tag is Intended For

However, there are instances, when using the canonical tag is very well justified. For example when you need to:

• Get rid of duplicate content within your own site

Thing is, when you have both example.com and www.example.com indexed by search engines, and they have identical content, this may lead to the duplicate content issue within YOUR OWN domain. By adding the canonical tag to one of these URLs, you tell Google not to take your non-canonical pages into account.

• Funnel all your link juice to one place

When you have more than one version of a URL indexed, your link juice may get distributed among several URLs. This hurts your link building. So, if there is no way you can set up a 301 redirect, use the canonical tag to steer all the PageRank to one page.

• Deal with the protocol issues

Some sites use the secure HTTPS protocol (e-commerce sites, for example). However, there may be an HTTP version of the same page indexed. In this case, using the canonical tag will help.

Canonical URL Plugins

Also, there are some cool plugins for different content management systems that allow one to create canonical URLs at ease. For example, the Canonical URL's plugin for WordPress, Magento Canonical Extensions or the SEO Canonicalization Plugin for Joomla.

So, all in all, what you should bear in mind is

-having control over your URLs' canonicalization is key to your site's high rankings

-there are different ways to specify canonical URLs, and the use of the canonical tag is not always justified

-specifying canonical URLs can be done manually or with the help of canonical URL plugins.