First off let’s view the rel=’canonical’ tag at a very basic level in order to understand it’s many uses and benefits. The term canonicalization means to convert data that has more than one representation and turning this into a single form, or standard. Ultimately improving an efficiency of various algorithms through reducing the requirement of repeated calculations.
Canonical web pages share the very same function as described above. When placing a canonical tag on top of a web page it simply states to the search engines where to find the original content, amongst different pages that contain similar content or simply duplicated content. Something that without search engines may not rank or even index. Therefore in order to ensure web pages that contain duplicated or highly similar content are designated with a canonical tag to help identify which is the master copy so-to-speak. This can especially be a re-occurring problem for large retailers who have many similar product pages that feature a different page for each product color, size etc…
“So how do I include this canonical tag you speak of”, I hear. Well, it can be included by simply adding a ‘link’ element within webpages ‘heading’ element, whilst adding ‘rel=canonical’ to the chain. This will target the original page that is considered the most important or original source of content. Because this will be attached to all of the offending duplicate and similar content pages, will direct the search engine crawlers to the original content and therefore ensuring the correct pages are indexed, with other not so important pages being allowed to be dropped from the index.
Duplicate content issues are only issues when they exist on the same website,this can happen easily depending on how your website is set up, but if you have the same content of a page which is located on different pages/URLs of your site out of necessity (for example if you have the same content under two different categories), then you’re going to have some issues.
Not only do you risk being penalized by search engines, but the search engines will only index one page between the two because they aren’t going to put two pages of the exact same content on the same site in their SERPs; so odds are when the search engine picks one to index, it may not be the one which you want appearing.
This can happen in a lot of different situations. One example is if you have two pages which exist with the exact same content on your site but which are meant for different interfaces. You may have a page of content which is for computer users accessing your site but then you may also have a page which has the exact same content on it but which appears slightly differently because it’s for mobile browser users.
In this modern age where everyone and their mother has a smartphone, a lot of sites have special versions of their sites or content which is mobile friendly. The problem is is that Google and other search engines will see these two pages of content as being the same. When it finds the two pages, it becomes forced to choose one or the other to index. This is why you want to use the canonical tag so that Google can understand that you recognize that you have two versions of the same content on purpose and that they each have a purpose but Google should recognize that one version is the canonical URL.
Here is an example of a complete canonical link:
The canonical tag is important in SEO, as a result. Choose which page of the content which you want the search engines to recognize, then place the canonical tag which looks like this:
<link rel=”canonical” href=”http://www.example.com/subdomainexample#1″ />
(the URL should be the page which you want indexed) within the Head tag of the duplicate pages.
Google will see this “hint” and recognize on the duplicate pages that they are simply duplicates of the canonical URL as designated with your canonical tag.
Therefore any webpage with this within the heading element is instructing the search engine crawlers that whatever is on this webpage originates from the following URL, therefore more valuable than the current webpage.
Some Important Facts:
Always try and generate Standardized Urls or Normalized Urls for your site.Make sure that all you links are consistent and uniformly kept with your homepage so they don’t end up with a serious of copies of the same page.If you have /home.asp and index.html pages, rewrite, that all the those other urls are 301 redirects to a single url so the search engines can follow the 301 and group them all together.Sometimes if you use a free host it is not possible to do any 301 redirects- contact your Web Host about this.What is the difference between a 301 Redirect and Canonical Links -Not much – a 301 Redirect can be used across different sites but a Canonical can only be used in the same domain, however, it can also be used with sub-domain of the same url. Confused? Here is a video to help
Now if you have duplicate content from two different domain names then it will not work. The Canonical code only works with sub domain names from a single top level domain. So if you have multiple pages on your website that lead to the same content this should hopefully solve this problem.
Now you know how what a canonical tag is and how to use one, let’s view the exact purpose and the benefits webmasters can benefit from.
1. As discussed, using the rel=’canonical’ tag allows the search engine crawlers to determine which page is the original content and therefore would be ranked higher. Product pages can often involve more than one page relating to the single product. So this will result in more than a single page containing the same content, even if it’s different but very similar the rel=’canonical’ is still encouraged by search engines.
2. Canonicalization can be used to help improve and tidy up website URLs, especially those that have more than a single home page appearing within the search engine results pages (SERPs). For example its common for webpages to have the following pages visible within the SERPs:
Both of these pages are treated as individual webpages. The introduction of a canonical tag can illustrate which one to treat only as the homepage. Otherwise both may be penalized and in effect not rank as well as if there was only a single page with the same content.
As a webmaster this is an issue that may crop up and become a problem. Or be able to enhance your site today, therefore it’s highly recommended to see where possible the rel=’canonical’ can be best put to use. Those currently operating with SEO agencies will no doubt already have these in place. Therefore try having a look over your site if this is the case to see if they are already in place or go hunting and see if you can see any well placed live examples.
Well, now that you have the Canonical URL Link Tag it is time to put it to good use. Start searching for any duplicate content pages you might have and get them taken care of fast. The sooner you do, the better the ranking you will have.