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The Canonical Tag and Canonicalization

When it comes to SEO, the tactics therein can not only be difficult to carry out, but are often difficult to understand as well. To this day, business owners and SEOs alike still struggle to get a firm grasp of the canonical tag, or URL. Often referred to as canonicalization, the process is set in place to avoid duplicate content and the issues associated with such. In other words, when site owners have multiple pages with similar content, they’ll place a canonical tag within the coding of their website to signal to search engines to ensure they’re not flagged as spam. While this is common practice, many SEO experts, and even Matt Cutts himself, will tell you canonicalization isn’t always necessary.

Considering the confusion and debate over canonical URLs, we’ve created a guide to canonicalization for those unsure of whether or not it’s necessary for their website. With this, let’s take an in-depth look at the canonical tag.

Suggested Reading

If you’re not worried about duplicate content, or you’re ready for more information on SEO, take a look at the pages we’ve provided below:

Canonical Definition

As you may have noticed, we’ve already used a few terms in regards to canonicalization: the canonical tag and canonical URL. Further, you also have rel canonical or rel=canonical—which is how the actual tag displays in the coding of a site. In short, all these terms refer to the same thing, or the same process: canonicalization. As defined by Moz, “canonicalization refers to the individual web pages that can be loaded from multiple URLs.” The process involves signaling to search engines that these pages are similar, in which one URL is tagged to tell said search engines which page should be served in search results.

The Issues (or lack thereof) with Duplicate Content

As mentioned, the point behind the canonical tag or URL is to avoid the penalties that can result from duplicate content. However, it may be surprising to hear that, unless the duplicated content is clearly there to manipulate search engines and attain keyword rankings, there’s really not much to worry about. For clarification, let’s take a look at some common reasons why a site might have duplicate content (the non-harmful kind):

  • Depending on the web user, they may type your URL with a www. or without it, and the browser they’re using will bring up the page either way. In many cases, the search engine will see these as two separate versions of a page. You can use the rel=canonical tag here to signal to search engines which page should be scanned.
  • Typical of an ecommerce site, users will be assigned their own session ID, which can sometimes be placed in the URL, creating a separate URL for the same page. These URLs will then be seen as duplicate content by search engines.
  • If you have a mobile version of your site, the URLs for each page may read, which creates multiple URLs for each page.
    • Real World Application

      To put things into perspective, let’s look at a real world example of some non-malicious duplicate content. Imagine you work in the financial services industry, and your website has a variety of pages that are required to have a specific set of terms and conditions provided on each page. As you can imagine, you could have 15+ pages with the same piece of content at the bottom of each. This is clearly non-malicious, and search engines will see it as such. In this case, a canonical tag is really not necessary.

      Why a Canonical Tag Might Be Necessary

      Though we’ve defined canonicalization and why it’s often used, it may help to look at the canonical tag as a way to tell search engines specific pages of your site are authentic. In essence, it’s used to tell the search engine which of the pages with duplicate content should be served in search results. While you usually don’t have to worry about duplicate content as long as it’s not malicious, there are certain cases where a canonical URL or tag is necessary.

      Given that SEO is all about ranking higher in search results, we all want each page of our website to perform well in search engines. However, if you have a couple of pages with very similar content on your site, search engines will have a difficult time deciding which page to serve up in results. To avoid this and any potential drop in rankings, the canonical tag is used to specify which page to serve—as mentioned above. This way, you can ensure the correct page is served and optimize it accordingly, known as the preferred URL. Of course, using the canonical tag can be just as confusing as trying to understand what it is.

      Using the Canonical Tag: Common Mistakes

      Using the canonical tag is no easy task. SEOs must be careful in implementing the tag on websites to ensure it’s used correctly and picked up by search engines. Considering how confusing the process can be, there are a few common mistakes we see quite often. Take a look below:

      • Setting the Preferred URL: For whatever reason, many site owners select their home page as the preferred URL when using the canonical tag, but in most cases, this will only harm your ability to rank in search results. The reason for this is any pages pointing to the homepage may not be indexed by the search engines.
      • Multiple Tags: Whether a result of negligence or the SEO software used, a single page with more than one canonical tag won’t be picked up by the search engine.
      • Placement: The rel=canonical tag must be placed in the of the pages coding. If it’s placed in the or anywhere else, it won’t be picked up by the search engine. Though it seems easy to avoid, you’d be surprised how common the mistake is.
      • Tags vs. Redirects: Canonical tags and 301 redirects have similar uses, but using one instead of the other in certain cases can pose a problem. Canonical tags should be used to deal with duplicate content, whereas a 301 redirect is best suited for when the architecture of your site has changed, say, moving content from one page of your site to another.

      How to Properly Use the Canonical Tag: rel=canonical

      As clarified in the common mistakes listed above, the canonical tag is always placed in the header of each webpage’s HTML coding. So, when adding the rel=canonical tag to a page’s HTML header, you first must decide which page will be the preferred URL and add the tag. In essence, the canonical tag looks something like this:

      While the process seems fairly simple, it could be a bit daunting for someone who’s never worked with the coding of their site. Fortunately, most content management systems will offer plugins to simplify things.


      While non-manipulative duplicate content shouldn’t harm your website’s ability to rank, using the canonical tag is still necessary in many cases. Even if you’re not penalized for the similar content, search engines will still need to know which page should be served up in search results. So, if you have two similar pages and prefer one to be served in search results, you’ll want to tag it accordingly, as well as optimize it for the resulting traffic. If you just have terms and conditions, or the multiple URLs mentioned earlier in this article, there’s probably not much to stress about.

      Tracking the Results of SEO and Site Changes

      As you make changes to your website and implement SEO strategies, it’s important to monitor any action you take to see how it affects your website. With StatCounter and our web tracker, you’ll have access to a range of metrics to help you determine how users are navigating through your site and much more. If you ever need assistance, you can contact StatCounter support by completing the form provided below.

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