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What are Canonical URLs and How Do They Impact SEO?

November 29th, 2023

A Canonical URL (or “canonical link”) is an HTML element used to prevent duplicate content issues within a website or across different websites. It helps search engines understand which version of a page should be treated as the primary or authoritative version. The canonical URL is essentially the preferred version of a webpage.

First lets get into what duplicate content is and how it can negatively impact your SEO rankings.

What is Duplicate Content in SEO?

Duplicate Content on Computer Monitor

In the context of SEO (Search Engine Optimization), duplicate content refers to identical or very similar content that exists in more than one place. This can be within a single website or across multiple websites. Search engines, such as Google, aim to deliver diverse and valuable results to users, and having the same content in multiple locations can create challenges and potential issues for both search engines and website owners.

How can duplicate content negatively impact my rankings?

Duplicate content can have several negative impacts on your website’s rankings in search engine results. Here are some ways in which duplicate content can adversely affect your SEO:

  1. Keyword Dilution: When the same content is spread across multiple pages, the relevance of specific keywords may be diluted. Search engines may have difficulty determining which page is the most relevant for a particular search query, potentially leading to lower rankings for all versions of the content.
  2. Confused Search Engines: Search engines aim to provide diverse and valuable results to users. If multiple pages with identical or very similar content exist, search engines may struggle to choose the most relevant version. This can result in the search engine ranking only one version or none at all.
  3. Backlink Dilution: Backlinks (links from other websites to yours) are a crucial factor in SEO. Duplicate content can lead to backlinks being spread across different versions of the same content, diluting the overall authority and impact of those backlinks.
  4. Crawl Budget Issues: Search engines allocate a limited “crawl budget” to each website, determining how often they will crawl and index its pages. Duplicate content can waste this crawl budget on non-essential pages, potentially causing important pages to be crawled less frequently.
  5. Penalties and Devaluation: While search engines may not penalize every instance of duplicate content, intentional or manipulative duplicate content can lead to penalties. Search engines may devalue the rankings of a site engaging in such practices.
  6. Poor User Experience: If users encounter the same content on different pages, it can result in a poor user experience. Users may become frustrated or confused, leading to higher bounce rates and potentially impacting the site’s overall performance.
  7. Canonicalization Issues: In the absence of clear signals indicating the preferred version of content, search engines may struggle with canonicalization. This means they may not correctly identify the primary version of the content, leading to ranking challenges.

To help mitigate the negative impacts of duplicate content, it is important to implement strategies such as using canonical tags to specify the preferred version, setting up proper redirects, and consistently managing and optimizing your website’s content structure.

Let’s look at how canonical URLs can help you prevent duplicate content from negatively impacting your SEO rankings.

How to Use Canonical URLs

Canonical URLs are an important tool in SEO for mitigating the negative impact of duplicate content. By using the canonical tag in the HTML head section of webpages, website owners can clearly specify the preferred version of a page when duplicate or similar content exists. This not only helps consolidate SEO signals like backlinks and authority to the authoritative version but also prevents penalties from search engines. Canonical URLs improve indexing efficiency, enhance user experience, and guide search engines in ranking the correct version, avoiding competition between duplicates.

Canonical URL Example

Let’s use a scenario that we run into often where a website has two very similar pages, each accessible through different URLs, in this example we will use common eCommerce URL structures:

  • Page 1:
  • Page 2:

To prevent potential duplicate content issues and specify the preferred version, you can use a canonical URL. In this case, you want to indicate that is the preferred version. Here’s how you might implement the canonical tag in the HTML code of both pages:

<!-- Canonical URL for Page 1 ( -->
<link rel="canonical" href="" />

<!-- Content of Page 1 goes here -->


<!-- Canonical URL for Page 2 ( -->
<link rel="canonical" href="" />

<!-- Content of Page 2 goes here -->

In this example:

  • Both pages reference the same canonical URL, indicating that is the authoritative version.
  • Search engines, when crawling these pages, will recognize the canonical tag and understand that the content of both pages is essentially the same, with being the preferred URL.
  • SEO signals, such as backlinks and authority, will be consolidated to the specified canonical URL, avoiding dilution across multiple versions.
  • If users access Page 2, search engines may still index it but should display the preferred version (Page 1) in search results.

Canonical URLs help guide search engines in understanding the relationships between similar pages and prevent potential SEO issues associated with duplicate content. It’s important to note that canonical tags are advisory signals, and search engines may still choose to index and display non-canonical versions in certain situations.

Reasons Why a Website Might Have Duplicate Content

Here are the five main reasons that we usually see a website with duplicate content:

Multi Language Website with Users Line Art
  1. URL Variations: Different URL structures or variations (www vs. non-www, HTTP vs. HTTPS, URL parameters) can lead to the same content being accessible through multiple URLs, causing duplication.
  2. Session IDs and Tracking Parameters: Inclusion of session IDs or tracking parameters in URLs for analytics purposes may create multiple versions of the same page in search engine indexes.
  3. Pagination and Sorting: Paginated pages or pages with sorting options can generate multiple URLs with similar content, causing unintentional duplication.
  4. Internationalization: Multilingual websites that offer the same content in different languages may inadvertently create duplicate content unless proper hreflang tags are implemented.
  5. Content Syndication: Websites syndicating content to multiple platforms or partners without using proper canonicalization may face duplicate content issues across different domains.

When we addresses these issues the process to correct them often involves implementing technical SEO best practices, such as using canonical tags, setting up redirects, and configuring parameters in webmaster tools. Regular audits and monitoring are essential to identify and resolve duplicate content issues for maintaining strong SEO performance.

How to Identify Duplicate Content On Your Website

Identifying duplicate content on your website is an important step in maintaining a healthy SEO profile and is something we do regularly for our clients. Here are several methods and tools you can use today to identify duplicate content on your website:

  1. Google Search Console: Google Search Console provides a variety of tools to help you monitor and improve your website’s presence in Google Search. The “Coverage” report can highlight issues like duplicate content, and the “URL Inspection” tool allows you to check the indexed version of a specific page.
  2. Site: Search Operator: Use the site: search operator on Google to find duplicate content within your site. For example, searching “your content” will show you all indexed pages with that specific content.
  3. Manual Site Audit: Conduct a manual audit of your website, examining key pages and their content. Look for identical or very similar content on multiple pages, and pay attention to URL variations.
  4. Specialized SEO Tools: Several SEO tools can help you identify duplicate content. Tools like Screaming Frog, Ahrefs, SEMrush, and Moz have features that can analyze your website for duplicate content issues.
  5. Google Analytics: Analyze your website’s performance in Google Analytics. Look for patterns in user behavior, such as high bounce rates on specific pages, which might indicate duplicate content problems.
  6. Copyscape: Copyscape is a tool specifically designed to find duplicate content across the web. You can use it to check if your content has been duplicated on other websites.
  7. XML Sitemap Analysis: Review your XML sitemap to identify duplicate URLs. A well-organized sitemap can help you spot patterns and potential issues.
  8. Check for URL Variations: Look for variations in your URLs, such as www vs. non-www, HTTP vs. HTTPS, or URL parameters. Ensure that your preferred version is canonicalized.
  9. Compare Meta Information: Examine the meta information (titles and descriptions) of your pages. Duplicate titles and meta descriptions might indicate duplicate content issues.
  10. Use Online Plagiarism Checkers: Online plagiarism checkers like Grammarly or Small SEO Tools can help you identify instances where your content may have been duplicated without your knowledge.

How Do I Know if My Website Is Using Canonical Tags?

To check if your website is using canonical tags, you can follow these steps:

  • View Page Source Code:
    • Open the webpage you want to check the canonical tag.
    • Right-click on the page (anywhere on the page) and select “View Page Source” or “Inspect” in your browser. This opens the developer tools.
  • Search for Canonical Tag:
    • In the source code, look for a line that resembles the following HTML code, The href attribute contains the URL of the preferred version of the page:
<link rel="canonical" href="" />
  • Use SEO Tools:
    • SEO analysis tools can help you quickly identify canonical tags across multiple pages. Here’s a general approach using Google Chrome’s built-in Developer Tools:
      • Right-click on the page and select “Inspect.”
      • Go to the “Elements” tab.
      • Use the search functionality (Ctrl + F or Command + F) and search for “canonical” to find the canonical tag.
    • Alternatively, SEO tools like Screaming Frog, Ahrefs, SEMrush, or Moz can provide comprehensive reports on canonical tags across your site.
  • Google Search Console:
    • Google Search Console provides information about canonicalization. Go to the “Coverage” report, and if there are issues related to duplicate content or canonicalization, it will be highlighted.
  • Check CMS Settings:
    • If you are using a content management system (CMS), explore the CMS settings to see if there are options to configure canonical tags. Some CMS platforms provide built-in features for managing canonicalization.

It is important to remember, the absence of a canonical tag doesn’t necessarily mean there’s a problem, especially if you have a small, straightforward website with no duplicate content concerns. However, for larger websites or those with dynamic content, implementing canonical tags strategically with an experienced SEO Company can help ensure you do not lose rankings due to duplicate content. Contact our team today for a free SEO Analysis and we can help you ensure your site avoids duplicate content.


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