What is Canonicalization? Using Canonical Tags to Improve SEO

When building your website, you want to indicate to Google and other search engines which versions of your content should appear in search results. The key to this is canonicalization, which uses specific HTML tags to label certain pages as indexable, while others will remain hidden from search engine crawlers.

In this blog, SEO Strategist, Kate Ganzha, will explain the importance of canonicalization SEO strategies and how to use canonical tags with practical tips.

What You’ll Learn

• What is Canonicalization?
• Reviewing Canonicalization Signals
• Do I Have Duplicate Content On My Site? Where?
• How to Implement Canonicalization Properly
• Common Mistakes with Canonicalization
• FAQs on Canonicalization

What is Canonicalization In SEO?

Canonicalization is an optimization technique used to prevent search engines from treating identical or very similar web pages as separate entities. This technique ensures that search engines understand which version of a page is the preferred or “canonical” one to index, reducing the risk of duplicate content issues.

By indicating which page is the original in your SEO strategy, canonicalization has the ability to lend more authority to that page while preventing potential cannibalization or even penalties for inadvertently using duplicate content.

This strategy is critical if you have multiple pages featuring the same or similar content. In addition to preventing issues with duplicate content, canonicalization can help with link equity by channeling the authority of similar or duplicate pages to the preferred version. It can also help optimize the crawl budget to enable faster indexing and ranking.

Another benefit of canonicalization is the ability to improve the user experience, as having a definitive page show up in search engines can eliminate any confusion among potential visitors to your website, directing them to the information they seek as soon as they seek it.

So, How Does Canonicalization Work?

1. Identification of Duplicate Content—Website owners identify pages with duplicate or highly similar content. Duplicate content can arise from various sources, such as printer-friendly versions, URL parameters, or slight variations in page URLs.
2. Canonical Tag Implementation—For the identified duplicate pages, website owners add a “canonical” link element in the HTML header of each page. This tag specifies the preferred or canonical URL of the content.
3. Search Engine Interpretation—When search engines crawl the website, they encounter these canonical tags. They use the information provided by the canonical tags to understand which page should be considered the primary or original version.
4. Indexing and Ranking—Search engines then index the canonical page and attribute its content and ranking signals to it. This helps in consolidating the SEO value of the duplicate pages onto the canonical page.
5. User Experience—From a user’s perspective, they still see duplicate pages, but behind the scenes, search engines understand which one to prioritize in search results.
6. Eliminating Duplicate Content Issues—By implementing canonicalization, website owners help search engines avoid the confusion of indexing multiple similar pages, which could otherwise lead to lower rankings or exclusion from search results.

Preventing Duplicate Content with Canonical Tags

The rel=canonical tag may look a bit strange, but it serves a key role in the world of SEO. It’s an HTML element that functions much like a citation.

Imagine it as a way to tell search engines, “This content isn’t original; the true source is found elsewhere.” This tag is a powerful tool to prevent search engines from treating similar content as duplicates, thereby helping you evade potential SEO penalties.

So, what does this tag actually look like? Here’s a representation:

It’s a <link> element with the rel attribute set to “canonical,” and the href attribute points to the URL where the genuine content resides.

Search engines will prioritize indexing and ranking that particular URL over any others containing similar content. This approach not only enhances the accuracy of search results but also helps you steer clear of duplicate content issues and potential SEO drawbacks. 

What Are Canonicalization Signals?

The canonicalization process relies on a variety of signals to help search engines like Google identify the preferred version of a web page. There are around 20 distinct signals that play a role in this determination. These signals include several factors:

1. Duplicates—Identifying duplicate content across the web.
2. Canonical Link Elements—The presence of canonical link elements in web page HTML.
3. Sitemap URLs—Information contained in XML sitemaps, which can specify canonical URLs.
4. Internal Links—How a website’s internal links are structured and which pages they prioritize.
5. External Links—The influence of external links pointing to a page.
6. Redirects—Use 301 redirects to permanently direct traffic from one URL to another.
7. Hreflang—Signals related to language and regional targeting for international websites.
8. PageRank—The distribution of PageRank, Google’s ranking algorithm, across various pages.
9. HTTPS > HTTP—Favoring secure HTTPS pages over non-secure HTTP ones.
10. Shorter URLs > Longer URLs—A preference for concise URL structures.
11. Original Content Source—Where content was first published or initially seen.
12. Site-Level Signals—Factors like a history of scraped content at the website level.
13. Pages > PDFs—Prioritizing web pages over PDF documents.

These signals collectively inform Google’s decision on which version of a page to assign as the canonical one.

The decision-making process is carried out by a machine learning system, which evaluates and weighs these signals to determine the most appropriate canonical version of a web page.

This approach ensures that users will receive the most relevant and high-quality content in their search results.

Do I Have Duplicate Content On My Site?

You might be thinking, “Do I really have duplicate content on my website? Is canonicalization even relevant to me?” Well, duplicate content can sneak onto your site without you even realizing it.

Let’s break down some common scenarios:

Region Variants

Let’s start with regional variations. If your website serves both www and non-www versions of the same content, search engines view them as distinct URLs with identical content. So, you’re dealing with duplicate content.

Device Variants

Another common scenario is device-related duplication. When your website offers different versions for mobile and desktop users, you may inadvertently create duplicate content.

Protocol Variants

If your site can be accessed via both HTTP and HTTPS, you’re providing the same content through different protocols, leading to duplicate content concerns.

Site Functions

Sometimes, site functionalities like sorting options or pagination can generate multiple URLs with the same content. Search engines might not distinguish between them, causing duplicate content issues.

Accidental Variants

If your URLs have variations in capitalization, trailing slashes, or query parameters, search engines may treat them as separate pages with identical content.

Non WWW and WWW Variants

URLs with and without the “www” prefix can be perceived as duplicates if not properly handled.

URLS and Trailing Slashes

Similar content accessed through URLs with and without trailing slashes can pose duplicate content problems.

URLs With and Without Capital Letters

Case sensitivity in URLs can lead to multiple variations of the same content being indexed separately.

Default vs. Alternative Versions

Default pages (like index pages) and their alternate versions can sometimes cause confusion for search engines, resulting in duplicate content issues.

URL Parameters

If you use URL parameters, like tracking codes or filters, it’s easy to generate multiple URLs pointing to the same content. This is especially common in ecommerce sites.

Scraped or Syndicated Content

If your website syndicates or scrapes content from other sources, it’s crucial to handle canonicalization correctly to avoid issues related to duplicate content.

In all these cases, the smart move is to implement canonicalization. This technique helps you direct search engines to the definitive, preferred version of your web pages, effectively resolving duplicate content concerns.

How Do Implement Canonicalization Properly?

There are a few different ways to implement canonical URLs.

Add Preferred Canonical URLs in Google Search Console

One way to establish a preferred canonical URL is through Google Search Console, a straightforward process that applies to your entire website.

However, it primarily addresses domain-specific issues, such as resolving the www vs. non-www URL preference. Keep in mind that this method exclusively impacts Google’s indexing and may not address other search engines.

Here are some steps you can follow to implement one or multiple canonical tags using Google Search Console:

1. Log into Google Search Console.

2. Access the URL Inspection Tool in the left dashboard menu.

3. In the top search bar, enter the URL you would like to inspect and make canonical.

4. Click “Test Live URL” to determine whether the designated page is indexable.

5. Click on “Request Indexing” button if the page is indexable and you want it to be the primary page.

6. If you notice any canonicalization issues when testing a URL, Google could provide an explanation to help you resolve them.

Use rel=canonical HTTP Header

Utilizing the rel=canonical HTTP header offers an alternative approach, albeit a more technically involved one.

This method entails configuring a name/value pair within the HTTP response. While effective, it requires advanced web development knowledge and may not be the most user-friendly option for everyone.

To manually add a rel=canonical tag to your website, take the following steps:

1. Choose the page you want to canonicalize. For example, you might have the following two URLs that contain the same content:

2. Add the rel=canonical tag manually to the meta tag within the designated page’s HTML header. The resulting tag would look like: <link rel=”canonical” href=”https://example.com/wordpress/seo-plugin/” />

Rely on 301, 302 and 303 Redirects

Redirects, particularly 301 redirects, are another way to influence canonicalization. They function as a “forwarding” mechanism, directing visitors from one URL to another.

For example, if someone lands on https://www.mysite.com/my-content, they will be automatically redirected to https://mysite.com/my-content.

However, it’s important to note that redirects are most suitable when you’re permanently moving a web page from one address to another, rather than for standard canonicalization purposes.

Try the Yoast Plugin

This method is user-friendly and doesn’t demand extensive technical expertise.

Popular SEO plugins like Yoast often provide easy-to-use interfaces for adding rel=canonical tags, simplifying the process for website owners and content creators.

Address Canonicalization Issues With International Websites

If you have a website targeting international audiences, you may use hreflang tags to translate your web pages into different languages.

Here, it’s crucial to ensure that your canonical and hreflang tags are for the same URL.

So, if you notice that you have conflicting hreflang and rel canonical tags, be sure to update the hreflang URL with the desired canonical URL to prevent potential content issues. In turn, both the original page and hreflang versions all support that canonical page.

JavaScript Considerations for Canonicalization

When working with a website that primarily uses JavaScript to render content, canonicalize the preferred pages within the raw HTML or, alternatively, you could apply it after JavaScript.

Otherwise, if canonical tags appear only in rendered Document Object Models (DOMs), search engines may struggle to crawl and index canonical pages.

Here is a checklist to help you diagnose certain canonicalization issues and resolve them:

• Check Canonical Tags on Each Page Type: Utilize Google Search Console’s URL Inspection Tool and other solutions to verify your website’s URLs and indexability, and address any issues that require correction.
• Verify Tag Placement and Syntax: The <link rel=”canonical”> tag must be properly placed on each canonical page, either directly within the HTML code or in another equivalent placement, depending on the type of page and the platform you use. Also, ensure the code is devoid of any typos or that your tags are for broken links.
• Identify Instances of Duplicate Content: Google Search Console’s “Pages” report can indicate if there are any duplicate pages you need to address. For instance, you might see pages labeled as “Duplicate, Google chose a different canonical” or “Duplicate without user-selected canonical.” You can also perform a “site:example.com” search on Google to see if multiple identical pages appear in search results.
• Review Server Configuration and URLs: You may also spot issues with server configuration when handling redirects to canonicalized pages, or you could experience issues with URL structure, such as conflicting www and non-www versions of your site, plus multiple HTTPS and HTTP versions you need to consolidate.

Common Mistakes With Canonicalization

Canonicalization is a powerful SEO tool, but it’s important to wield it correctly. Here are some common mistakes to avoid when implementing canonicalization:

1. Blocking a Canonicalized URL with robots.txt

The rel=canonical tag is about guiding search engines, not restricting access. When you block the canonical URL, you hinder search engines from understanding your preferred version, potentially causing indexing issues.

2. Setting a Canonicalized URL to “noindex”

Similarly, setting the canonicalized URL to “noindex” contradicts the purpose of canonicalization. This meta tag tells search engines not to index the page, essentially nullifying the canonical tag’s intent. Ensure that your canonical URL is set to “index” to maintain its SEO value.

3. Setting a 4xx HTTP Status Code for a Canonicalized URL

Using a 4xx HTTP status code, like 404 (Not Found), for a canonicalized URL is a mistake. Search engines rely on a 200 (OK) status code to understand that the page is valid and should be indexed. A 4xx code can signal a broken or missing page, which conflicts with canonicalization.

4. Canonicalizing All Paginated Pages to the Root Page

Canonicalizing all paginated pages (e.g., page 2, page 3) to the root page (page 1) is not advisable. Each paginated page may have unique content, and canonicalization should reflect that. Instead, use rel=”prev” and rel=”next” tags to indicate the relationship between paginated pages while specifying the canonical URL for each.

One case study from SEO auditing tool Sitebulb showed how a client of theirs benefited from improved SEO by identifying issues with pagination. Specifically, a pharmaceutical company conducted an audit using Sitebulb that found negative canonical tags SEO impact due to their implementation on paginated pages for the client’s press release newsroom.

To properly canonicalize the newsroom, Sitebulb recommended a self-referential canonical tag to help Google index content on paginated URLs, which looked like this:

5. Using the URL Removal Tool in Google Search Console

Using the URL removal tool in Google Search Console to remove canonicalized URLs can lead to content de-indexing. This tool is designed for temporary removals, not for managing canonicalization. Utilize canonical tags and proper directives instead.

6. Not Keeping Canonicalization Signals Consistent

Inconsistent canonicalization signals confuse search engines. Ensure that all signals, including canonical tags, HTTP headers, and redirects, align with each other. Mixed signals can result in search engines not recognizing your preferred version correctly.

7. Not Using Canonical Tags with hreflang

If your website serves international audiences with hreflang tags, don’t forget to integrate canonical tags alongside them. This combination helps search engines understand the relationship between regional or language-specific variations of your content, ensuring the right version is displayed to users.

8. Having Multiple rel=canonical Tags

Avoid having multiple rel=canonical tags on a single page. This can cause ambiguity for search engines. Always have one clear canonical tag specifying the preferred URL. Multiple canonical tags can lead to unpredictable indexing outcomes.

9. Adding the rel=canonical in the <body> Not <Header>

Canonical tags should be placed in the HTML <head> section, not in the <body> of a webpage. Placing them in the <head> ensures that search engines can readily identify and interpret the canonicalization directive. Placing them in the <body> may not achieve the desired results.

10. Using canonicalization with an outdated domain

When changing your website’s domain, you may neglect to make canonical tags on your new domain self-referential, instead having them redirect to the old domain.

This happened to a real estate client, who had an issue ranking for various keywords with a new website. During this time, the site saw only 154 keyword rankings, 24 of which were in the top 10 positions, while the remaining 130 were in positions 11 through 100.

During an audit, we discovered that all canonical tags across the site pointed back to the outdated domain.

Based on Sitebulb’s recommended fix, the company saw a positive canonical tags SEO impact when making all canonical tags self-referential.

These results included a more than 320% increase in rankings, with 65 keywords ranking in the top 10 results and 659 showing up in positions 11 to 100.

The Broader SEO Benefits of Proper Canonicalization

The right approach to canonicalization can lead to better SEO in the long term. Resolving various issues can ultimately lead to significantly higher rankings in different ways.

The following are some of the main benefits of canonicalization for SEO:

• Increased overall visibility and indexability for pages that serve as the main versions of pages
• Consolidated link equity as pages with authority retain that authority, whereas duplicate or similar pages might otherwise lead to more unevenly distributed equity
• The more people find and engage with your canonicalized pages, the higher these pages will rank due to a better user experience

It’s also possible to integrate canonicalization with other types of SEO strategies, namely on-page SEO components. In addition to canonical tags, you should optimize your domain name and slugs with relevant keywords, when possible, incorporate optimized H1 and other headers on your pages, title tags and meta descriptions that appear on Google, and natural keyword instances within your content. Also, interlinking can further assist with link equity as your pages link to each other across the website.

Like other SEO efforts, you should consistently track the canonicalization SEO impact of your strategy using tools like Google Analytics 4 and Google Search Console. For instance, you might measure keyword rankings, organic traffic, click-through rates, and conversions, all of which could indicate the visibility of your pages in Google search results.

FAQs About Canonicalization

1. When should I use a canonical tag instead of a 301 redirect?

Use a canonical tag when you want to specify the preferred version of a page with similar content, but you don’t need to change the URL that users see. Use a 301 redirect when you’re permanently moving a page to a new URL, and you want both users and search engines to be directed to the new URL.

2. Can I have multiple canonical tags on a single page?

No, it’s not recommended to have multiple canonical tags on a single page. Having multiple conflicting canonical tags can confuse search engines and may not yield the desired results. Stick to a single, clear canonical tag to specify the preferred URL.

3. What are common mistakes to avoid when using canonical tags?

Common mistakes include blocking canonicalized URLs via robots.txt, setting canonicalized URLs to “noindex,” and not keeping canonicalization signals consistent across various elements. 

4. Are canonical tags necessary for every type of website?

Canonical tags are particularly useful for websites with duplicate or similar content issues. However, not every website will face these issues. It’s essential to assess your site’s content structure and use canonical tags as needed to improve SEO.

5. Is canonicalization relevant for mobile websites?

Yes, canonicalization is relevant for mobile websites. If you have mobile and desktop versions of your site with similar content, canonical tags can help search engines understand the relationship between these versions and rank them appropriately.

6. Does Google penalize for incorrect canonicalization?

Google doesn’t penalize for incorrect canonicalization, but it may lead to SEO issues. Incorrect implementation can result in the wrong page being indexed or ranking lower. It’s essential to use canonical tags correctly to avoid such issues.

7. How do I monitor the effectiveness of my canonical tags?

To monitor the effectiveness of canonical tags, regularly check your website’s index status in Google Search Console. Ensure that the canonical URLs are being indexed as intended. You can also use SEO tools to analyze your website’s canonicalization and identify any potential issues that need correction.

8. Why does Google sometimes ignore the canonical URL?

Google may ignore your canonical tag if it doesn’t trust it, often due to significant content differences between canonical and alternate URLs, inconsistent internal linking, or technical issues like unnecessary 301 redirects. If you link to the non-canonical version, Google may choose a different URL to index. To avoid this, ensure your canonicals are clean, content is consistent, and internal links point to the correct URLs.

Start Improving Your SEO Now

Understanding canonicalization is crucial for optimizing your website’s search performance. Failing to grasp this concept may restrict your site’s visibility in search results, but Ignite Visibility has you covered. 

The digital marketing company is known for its outstanding SEO services. From technical SEO to content creation, 0ur digital marketing experts can help you rank high in search engine results.

Here are some of the specific ways we can help:

• Identifying canonicalization issues such as multiple canonical tags or redirects to outdated domains
• Resolving issues with proper implementations
• Continuous tracking of efforts to gauge impact
• Continuous optimization of other SEO elements to maximize rankings, traffic, and conversions
• Integration into other digital marketing solutions

Ready to get started?

Learn more about our SEO services here and contact us now! While you wait, start implementing canonicalization across all your pages to avoid duplicate content problems.