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What Is Canonicalization? How Does It Work?

A Guide to Detecting and Fixing Canonical Issues in SEO

In today’s blog post, we’re going to take a close look at canonicalization SEO and explain why you should be interested in it.

Following best SEO practices is essential for all commercial webmasters today. Without an effective SEO strategy, it’s almost impossible to rank well for popular key phrases. Local SEO is of particular importance to businesses with a physical presence whilst specialist e-commerce SEO (such as Shopify SEO) is crucial to online operators. And, if you truly want to shine in the digital space (whether you run a physical or online business), you need to learn about SEO canonicalization best practices too.

Issues with canonical tags can seriously impact search engine rankings for all types of websites. Here at MAM, we have noticed an increase in canonical URL issues in recent years, issues that can easily be solved if you know what to look out for and what type of action to take. The sooner you master website canonicalization, the sooner you will be able to achieve higher rankings for key content pages on your site.

Canonical Tag 101

A canonical tag, sometimes referred to as a canonical link, is a type of HTML tag that defines a canonical relationship between content on the page where the tag is placed and content on the page to be found at the URL specified in the rel attribute value (this URL is for the page where the preferred/original version of the content appears).

The primary purpose of a canonical tag, which is in essence simply a link tag with a canonical URL in the rel attribute, is to avoid being penalised for duplicate content. When multiple versions of the same content exist on multiple pages of your website, search engine crawlers don’t know which pages to index. In such cases, all pages containing the content in question may be penalised and either appear lower in search engine results pages (SERPS) or, worse still, not be indexed at all. Canonical tags can solve this problem by clearly identifying the canonical version for search engine crawlers.

Common Causes of Canonical Issues

In the simplest terms, the cause of all canonical issues is the presence of multiple copies of the same content, either on a single website or a group of websites (on multiple pages), with no clear indication as to which is the original/preferred/ canonical version. However, this definition is of little practical help to us when considering possible canonicalization SEO solutions: in order to find effective solutions, we first need to identify the root cause of our canonical URL issues, i.e. what action did we take that led to the problem occurring in the first place. Other than the accidental publishing of duplicate content due to an oversight, the most common root causes of canonical issues are:

  • HTTP vs. HTTPS – If you have recently implemented HTTPS on your website, without using redirects, you will find that Google (and other search engines) treat the HTTP and HTTPS addresses as two separate versions.
  • WWW vs. non-WWW – If there is both a WWW and non-WWW version of your website live, both versions will be indexed by Google, which could cause serious duplicate content issues.
  • URL Parameters – Many of the most popular CMS platforms make extensive use of URL parameters. While the information being passed in these parameters is valuable, such as users’ preferred sort options and SEO tracking data for individuals, URL parameters can cause significant duplicate content issues if each URL they create is considered a separate page by search engine crawlers.

In all of these cases, it is possible to resolve the issues in question through the judicious use of canonicalization SEO techniques or by changing the way that your website is currently configured. In some cases, you may find a 301-redirect preferable to a canonical tag, which is something we will talk about later, in the section entitled ‘Resolving Canonical Issues’.

Identifying Canonical Issues

Knowing about canonicalization SEO in theory can only take you so far. If you would like to take advantage of the benefits it has to offer, you will first need to determine whether your website has any existing canonical issues. There are several ways to achieve this goal, some of which are more effective than others:

  • Manual Testing – If you want to test for basic HTTP/HTTPS and WWW/non-WWW canonical issues, you can do so manually, i.e. by typing each address into your web browser. If you have redirects set up properly, you will find yourself landing on the same URL no matter which version you type into the address bar. On the other hand, if you type in a URL variant and the URL does not change to reflect the preferred version, it means you have not been redirected. More importantly, it means that Google and other search engines will treat each URL variant as a separate page.
  • Testing With SEO Tools – There are a number of online SEO toolsets that include useful functionality if you are looking for website canonicalization issues. Toolsets such as Moz, Ahrefs and SEMrush can all be used to identify duplicate content issues due to canonical tag errors or omissions.
  • Testing With Specialised Software – As an alternative to online SEO toolsets, some of which require users to pay an annual subscription fee, you may wish to install and use SEO spider tool software such as Screaming Frog instead. With Screaming Frog’s functionality, which includes the ability to view all pages of a website with their specified canonical URLs in one place, it is possible to identify potential issues more easily.
  • Google ‘Site: Search Term’ Searches – A quick and easy way to find duplicate content/canonical URL issues for specific content is to take a sentence from the content and search for all occurrences on your website. To do this in Google, simply enter your chosen sentence in speech marks, then press the spacebar once before entering ‘site:yoursitename.com’, replacing ‘yoursitename.com’ with the address of your website (excluding the WWW prefix). If the search results highlight multiple occurrences, with no associated canonical tags, you should rectify this issue without delay.
  • Google Search Console – The Google Search Console can be used to generate reports that highlight any duplicate content with missing canonical tags on your website. If you wish to take advantage of this functionality, you can get all the help you need in the console’s official documentation.

Whichever method and tools you decide to use, the first thing you will want to do should you uncover any canonical issues on your website is to resolve them, a topic we discuss next.

Resolving Canonical Issues

Once you uncover a canonical issue with your website, you will naturally be keen to resolve it as soon as possible. The best way to do this will depend on the nature of the issue you have uncovered. Accepted canonicalization best practices for specific issues include:

  • HTTP/HTTPS and WWW/non-WWW Issues – The simplest way to deal with these issues is to use site-wide 301 redirects. However, if you have a reason to avoid redirecting visitors from one version to another, you may use canonical tags instead. When considering canonicalization vs. 301 redirect choices in general, we only suggest using a canonical tag if you have a valid reason for wanting visitors to be able to see the non-canonical page/s.
  • Localisation Issues – With the correct use of Hreflang annotations and canonical URL tags, you can overcome any issues caused by localisation on your website.
  • Canonical Tag Errors – Some CMS platforms occasionally create incorrect canonical tags. In such instances, we recommend manual correction as well as reporting the error to your CMS provider.

For assistance with any other type of website canonicalization issues you may encounter, please don’t hesitate to call or message us.

Ongoing Monitoring and Testing

Fixing any and all canonical errors that you discover on your website is a great start but if you want to keep the canonicalization SEO advantage that you have established, you should implement ongoing monitoring and testing practices for the future. These practices should include regular site-wide checkups, using your preferred SEO toolset or software solution.

User Experience Considerations

It is of vital importance that you implement your canonicalization SEO strategy in a user-friendly manner. Consider how the tags you add may affect user experience before actually adding them.

More Resources

If you’re looking for more information on canonical tag implementation or canonical SEO issues in general, you can check out Google’s official documentation. You can also head straight to the troubleshooting section if you desire.

The main thing to bear in mind when considering website canonicalization issues is that a consistent approach will yield the best results, which should include adding self-referential tags on canonical pages. Whatever approach you choose, we recommend acting quickly to protect your search engine rankings and to contact us if you require any professional assistance. We offer a full range of SEO services, covering everything from canonical issues to advanced social media marketing strategies.

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