Canonical Issues: How to Find & Fix and Avoid Them

Canonical Issues: How to Find & Fix and Avoid Them
Recognizing canonical issues is your first step towards resolving them efficiently. As with any other SEO strategy, you must equip yourself with the right knowledge, take proactive steps to avoid common pitfalls, and keep a close eye on your implementation.

Let’s understand what a canonical issue is and explore how to deal with canonical issues. But before, it is required to understand what actually is a canonical tag.

What are Canonical Tags?

Consider this scenario - you have a product listed under multiple categories on your e-commerce site, each having its dedicated URL. The product description remains the same, thus creating duplicate content. Here, a canonical tag comes into play, indicating to the search engine your preferred URL (canonical URL) for indexing and ranking.

A canonical tag is a snippet of HTML code inserted into the web page's header section to tell search engines which version of a duplicate page you want them to rank in their search results. 

Synonymous to rel=“canonical”, this tag is quite a powerful tool to help you deal with duplicate content and canonical issues head-on.

After you identify duplicate content on your site, choose the page version you want search engines to index and rank - your 'canonical' URL. In the <head> section of your HTML of duplicate pages, add the link tag, <link rel="canonical" href="preferred-URL" />. Replace 'preferred-URL' with your chosen canonical URL and implement this across all duplicate URLs.

two webpages

Canonical tags help in consolidating link signals. By specifying the canonical URL, all the links, content metrics, and ranking power of duplicate pages are credited to the canonical version.

Also, a well-planned canonicalization strategy helps search engines in focusing their crawl budget on unique pages, leading to better indexing.

What are Canonical Issues?

A canonical issue arises when search engines are unable to determine the 'most preferred' version of a page or a set of pages on your site. This creates hiccups in indexing, affecting your site's search engine ranking. 

The root causes of canonical issues include:

🚨 Duplicate content: When the same content appears on multiple URLs, it leads to confusion for search engine crawlers to decide which version to show in results. Some common situations involve content replication across different site areas like http/https or www/non-www versions, mobile & desktop versions, replicated content across subdomains, URL parameters generated by CMS or on-site filters, and session IDs created for analytics tracking.

🚨 Copy-pasting content: Copy-pasting content across multiple sites can trigger a canonical issue. While it's typical for syndicated or shared content, it’s crucial to manage these scenarios effectively.

🚨 URL structure changes: When you modify URLs for a better site structure or UX, you have to make sure to manage old URLs to prevent canonical issues.

🚨 Improperly configured rel=canonical or 301 redirects: These signals tell search engines about your preferred version of a page. Incorrect implementation may cause canonical issues.

Canonical issues need immediate attention because if your page versions are getting backlinks independently, it distributes the link equity among them, diluting the ranking power they could generate collectively.

Moreover, duplicate content or multiple URLs can lead to a confusing and inconsistent user experience, which can harm brand reputation and conversions. Also, search engines might rank the inferior page version, which can lead to a decline in website traffic.

You may want to read: 301 Redirect or URL Canonicalization 🤔

How Can You Determine If Your Site Has Canonical Issues?

Finding out if your site is plagued by canonical issues can be tricky, but it's a crucial step in maintaining a robust SEO strategy. 

Here are some common indicators:

🚩 Errors in canonical elements: Check for tags pointing to non-existent pages, tags forming chains, or tags pointing to redirected URLs. 

🚩 Misconfigured server: Using multiple URLs, running duplicate versions of your site, or having URLs serving both HTTP and HTTPS versions are common misconfigurations that can cause canonical issues. Keep in close contact with your web developer or hosting provider to ensure your server is configured properly.

🚩 Malicious hacking: In some cases, malicious hackers could infuse your site with duplicate content, causing canonical challenges. Regular website audits and keeping your website security up-to-date can help prevent this.

More importantly, conducting regular site audits allows you to detect canonical tag issues. For SEO audit, you can use Seomator's free audit tool. Helping you understand the current status of canonical issues and other on-page SEO requirements on your site, the Seomator audit tool also provides actionable insights and solutions.

SEOmator audit tool

10 Best Practices to Avoid Canonical Issues

Leveraging canonical tags using the best SEO practices elevates your website on its journey to top search engine results. It simplifies your website’s map for search engines, efficiently directing them towards the content you want to showcase.

Here are some helpful tips to avoid canonical issues before they have a chance to occur:

01. List Canonical URLs Only in Your Sitemap

Including canonical URLs only in your sitemap is a practical way to tackle canonical issues. Sitemaps provide search engines with a roadmap of your website, helping them crawl and index your content more efficiently.

Create a sitemap that includes the URLs of all preferred pages, also known as canonical URLs. When you create your sitemap, make sure not to include the URLs of any pages that are integral duplicates of others. This includes near-duplicate pages identical in every way except, perhaps, for one or two words.

Your sitemap should reflect your website's current state, meaning as you add, edit, or delete pages, your sitemap needs to reflect these changes. Regularly updating your sitemaps ensures that only your latest, most unique content is visible to search engines.

02. Ensure Other Sites Use Canonical Tags When Publishing Your Content

Good content deserves good exposure. But, in the process of wider circulation, one must not overlook the potential hazard - duplicate content. More often than not, this happens when your content gets published on other sites, whether it's guest blogging or content syndication. 

Ensure that the site republishing your content includes a canonical tag in the HTML that points to the original content on your website. Communicate this requirement to the republishing website during your content-sharing agreement to safeguard against possible SEO penalties.

For instance, if another website is publishing your article, this is how the canonical tag should be included in the <head> of their HTML:

<link rel="canonical" href="" />

By doing so, they acknowledge your content as canonical, regardless of which web page appears on search results. This way, your SEO strategies stay intact, even as your top-quality content travels across the expansive digital ocean.

03. Point to a Crawlable and Indexable URL

One common issue with canonical tags is pointing them to a URL that search engines cannot crawl or index. If search engines cannot access or understand the page, all the SEO value you hoped to consolidate via the canonical tag will be futile.

Check your robots.txt file to ensure the canonical URL is not disallowed. Use Google Search Console or SEOmator’s Free SEO Audit Tool to detect any potential crawl errors.

Lastly, make sure the canonical URL isn't set to noindex, as this will prevent search engines from indexing the page.

Implement these measures to ensure you avoid or rectify situations where canonical tags point to a URL that can't be crawled or indexed.

04. Don’t Create Canonical Chains

Another common canonical issue involves creating canonical chains. A canonical chain occurs when a canonical tag points to a URL that itself has a canonical tag pointing to another URL. This complex setup can confuse search engines and create issues in assigning authority to the correct URL.

To fix a canonical chain, make sure each page’s canonical tag points directly to the canonical version of the page, not to another duplicate page with a different canonical tag. 

05. Don’t Point to a URL that Returns a Status Code Other Than 200

302 redirection

Your canonical tags should always point to a URL that returns a HTTP 200 status code. This code signals that a page is working as expected. 

If a URL returns a status code indicating an error (such as 404) or a redirect (like 301 or 302), you can jeopardize your canonicalization efforts.

Regularly audit your website for broken links and pay attention to URLs that redirect. Both 301 (permanent redirect) and 302 (temporary redirect) status codes can disrupt the canonical tag.

You may want to read: 13 Common HTTP Status Codes + Explanations

06. Specify the Correct Domain Protocol

Your website may exist under two types of protocols: HTTP (Hypertext Transfer Protocol) and HTTPS (Hypertext Transfer Protocol Secure). 

While the former is less secure, the latter protocol provides encryption and secure identification of the network's servers, a feature requisite for websites seeking users’ data. Therefore, Google recommends using HTTPS, and so do we.

To avoid canonical issues, ensure you specify the correct protocol. HTTPS pages should reference HTTPS pages, and similarly, HTTP should reference its same kind. A mixed setup can confuse search engines and lead to lost page rank. So, verify it before the storm hits!

07. Use rel="canonical" in HTTP Headers

When we talk about canonical tags, instinctively we picture the tag nestled within our web page's head section. However, you can also deploy canonical tags in HTTP headers. 

Especially handy for non-HTML files (like PDFs), placing rel="canonical" directly in your HTTP headers allows search engines to crawl and correctly handle these documents.

Here's how an HTTP response with a canonical tag looks:

HTTP/1.1 200 OK
Link: <>; rel="canonical"

This tactic allows you to adopt a more inclusive approach, transparently communicating with search engines about your SEO game plan, even for documents other than HTML.

08. Decide Between Trailing Slash or Non-Trailing Slash URLs

Consider the URLs "" and "". While they seem identical to us, search engines consider them as separate entities. So, you must standardize your preference and stick with it throughout your website. Either is fine, but consistency is the key!

Decide at the onset whether to use a trailing slash or not. This decision should apply to how you internally link pages on your site, your canonical tags, your sitemap - in essence, each corner of your website universe.

This consistency helps search engines crawl and index your site more efficiently, minimizing the risk of any canonical confusion.

09. Decide Between Non-WWW or WWW URLs

www and non-www versions

While not directly a canonical issue, not maintaining consistency between non-WWW and WWW versions of your site can split your SEO value. Decide which version you want to use and then enforce it through a 301 redirect.

Keeping a clear, one-path rule can divide and rule potential canonical issues, allowing search engines to crawl, comprehend, and cater to your site in the best possible way.

10. Use Absolute URLs

An absolute URL contains the full-length information required for a document, making it easy for search engines to understand and users to bookmark. They look something like this:

On the other hand, a relative URL provides only the path to the document: /dir/page.html. If your site's canonical tags use relative URLs, they may lead to canonicalization errors.

The SEO best practice here is to use absolute URLs across your website, especially in canonical tags. This practice eliminates ambiguity, making it crystal clear for search engines, aligning with your SEO strategy, and keeping canonical issues at bay.

11. Conduct SEO Audits Periodically

It is also very important to detect canonical tag issues in order to solve them. Performing regular site audits allows you to detect such problems. For SEO audit, you can use Seomator's free audit tool. Helping you understand the current status of canonical issues and other on-page requirements on your site, the Seomator audit tool also provides actionable insights and solutions.

Final Thoughts

By correctly using canonical URLs, you are making the most out of your SEO efforts. They're like a guiding star for search engine crawlers, leading them to your choicest content and preventing them from wasting time (and crawling budgets) on identical or ‘near-duplicate’ content. Therefore, the importance of canonical URLs for SEO cannot, and should not, be sidelined.

An occasional overlook, a misplaced slash, or an unintended redirect can arise as bumps on the road to SEO success. By regularly auditing your canonical tags, you can nip such problems in the bud. Rectification is as important as implementation!

We hope that the knowledge and insights you've gained on common canonical issues and how to fix them will serve you well in your journey to achieve SEO success!

You might also want to read:

- How to Find Internal Links to a Page

- Orphan Pages: How to Find & Fix Them

- What is a Link Farm? - Why Should You Not Rely On It?