What Are Canonical Tags and Why Are They Used?

Search engines hate duplicate content. That’s because multiple copies of the same content make it difficult for search engines to choose which version of the page should be indexed. This is why Google supports the use of canonical tags. But what are canonical tags and how can they resolve duplicate content issues?

What Are Canonical Tags

An illustration depicting the need for canonical tags

A canonical tag is a piece of code that helps search engines identify the master copy of a webpage. If search engines find similar content on different links, a canonical tag or code can tell a search engine which URL must be given primary importance.

Why Are Canonical Tags Important?

Canonical URLs inform Google and other search engines to crawl your website and indicate what content needs to be indexed under what URL if you have duplicate content on your website. 

They help you specify which URL you want Google to index and rank

Canonical URLs help Google identify which URLs that you want your audience to see when they search for your pages. For example,

You can the highlight all coffee mugs on your website using


instead of


Using canonical tags makes your website’s search results and URLs look clean.

They simplify tracking metrics for a single product/topic

When you have a variety of URLs, it becomes more difficult for the search engine to collect consolidated metrics for all of your content. By using canonical URLs, you are able to keep things clean and organized for every single piece of content on your website. If you want to report performance accurately and want to take advantage of analytics, using canonical tags is a must.

They consolidate link signals for similar or duplicate pages

Canonical URLs can help search engines consolidate all of the information that you have for individual URLs into one authoritative URL. If you repurpose your content and publish it in other domains, using canonical URLs will help you consolidate page ranking for your preferred website instead of splitting them across multipole domains. It will prevent duplicate content from competing for traffic across different websites.

When Should You Use Canonical Tags?

There are many situations where canonical tags can be used effectively. The most common scenario is if you repost existing content or if you post the same content across multiple domains. It helps search engines identify which domain should get priority in the search engine results and avoids negative impact on SEO.

Reposting Content

If you post content in more than one domain or post the same content across multiple pages of the same website, using canonical tags is a must. Instead of simply linking your new reposted content to the original content and hoping that the site visitors go to the primary page, using a canonical tag will help your audience go to the main page at one go.

Syndicating Content

A common marketing strategy is to syndicate any existing content from other websites. While it is a practice that can help expand your brand awareness, it also means that the same content is spread across multiple pages and it makes it difficult for the search engine to identify which page to rank higher than the rest. By using canonical URLs, you do not compromise the search authority of your websites and also correctly rank your pages.

Using Several Link Variations

It is common for e-commerce websites to use various hierarchies and URLs as the websites change. When displaying different categories of products or services on your ecommerce website, you may be showing the same products but with different URLs and images. By using canonical tags, you ensure that your pages are directed to the top pages for the appropriate tags.

Accidentally Duplicating on Your Website

Not all website owners post duplicate content on their websites intentionally. There are many situations where content may be duplicated on your website unintentionally. The most common situation is when you have separate links for HTTP and HTTPS. Your pages may be flagged as duplicates if you have the same SEO meta descriptions and titles even if the content itself is different on both pages.

301 Redirect Vs. Canonical

Like with most SEO practices, there are guidelines on how to manage redirections by Google. There are clear guidelines for how to manage redirections and what each redirection method communicates to the search engine. If you use a 301 redirect, it means that the page has been moved permanently. A SEO redirect indicates that the older page is removed from the index and any SEO credit that was due to it will be redirected to the new page instead.

A canonical tag on the other hand signals the search engine that the same content has multiple versions and whichever page has the canonical tag should be attributed as the original or the “real page”. Only the original page is indexed by Google. Duplicated pages will be kept on your website but they will not be indexed by the search engine.

How to Implement Canonicals

There are five ways to approach canonical tags. These methods are known as canonicalization signals. Here are the five ways to implement canonicals that you should make use of.

By using a 301 redirect

When you use 301 redirects, you are essentially directing traffic away from duplicate URLs and only the canonical version receives traffic. You can choose which URL should be receiving the traffic by using canonical tags and all of the duplicate urls will redirect to the same page.

By using rel=canonical HTML tags

You can make use of SEO plugins like Yoast to self-reference tags and they will be added to your page automatically. You can use the Yoast SEO plugin and use the Advanced section on each page to manually add tags for your content. Adding a tag will automatically inform search engines, which page should be indexed and which pages should be ignored.

By using canonicals in sitemaps

According to Google’s guidelines non-canonical pages should not be included in the sitemaps. You should only include canonical URLs on your sitemap. It is a simple way to define canonicals for any website and sitemaps are the best way to let Google know which are the most important pages on your site.

By using canonicals in HTTP headers

If your URLs contain documents like PDFs, you will be unable to place canonical tags in the header section. However, you can create HTTP headers to set canonical tags just like standard webpages. You can follow this practice for non-PDF and it is an alternative to adding tags within the content.

Best Practices for Canonical URLs

While canonical tags are easy to implement, they need to be used correctly. Here are the four best practices for canonical URLs that you should follow for your website.

Use the correct domain protocol (HTTPS vs. HTTP)

If you recently switched to SSL, you need to ensure that you do not declare non-SSL urls in your canonical tags. Otherwise you will need to add tags for both HTTP and HTTPS equivalents of the same page. Always use the correct domain protocol as it avoids confusion and unexpected interactions.

Use self-referential canonical tags

Self-referential canonical tags are used on pages that point to themselves. Most modern content management systems make use of self-referencing URLs automatically so it is something you may not have to worry about. However, if you have a custom CMS, you may need to add your self-referencing URLs manually.

Use absolute URLs

Using absolute URLs ensures that the search engines interpret them correctly. You should not use relative paths when using canonical tags and using the full URL is recommended when setting up your tags.

Use only one canonical tag per page

If you have multiple canonical tags on a single page, Google will ignore both of them. You should avoid posting duplicate canonical tags to avoid indexing issues on search engines.

Canonical Mistakes You Should Avoid

There are some misunderstandings that website owners have when it comes to implementing canonial tags. As a result, they end up making several mistakes. Here are the biggest canonical mistakes that you need to avoid.

Blocking the Canonicalized URLs

The robots.txt file of your website lets Google know which pages need to be crawled. If there are no canonical tags in these pages, they will be blocked and will be unable to transfer any link-equity to the canonical pages form the non-canonical counterparts.

Having Multiple rel=canonical Tags

If you have multiple canonical tags, they will end up being ignored by Google. In most cases this happens because tags are inserted into a system at different points in time and mistakes can happen when adding them to your pages. Cross-checking proper tag usage is a must if you do not want it to adversely affect your SEO.

Canonicalizing all paginated pages to the root page

You should always use self-referencing canonicals on all of your paginated pages. You should not canonicalize paginated pages to the first paginated page of a series. Making use of rel=prev/next tags for pagination is also recommended even though Google no longer uses them, but other search engines do.

Not Using Hreflang with your Canonical Tags

You need to use the hreflang tags to specify the language and geographical targeting of your webpages. According to Google’s guidelines it is important to specify the canonical page with the appropriate geographical language. According to Google’s guidelines, you need to “specify a canonical page in the same language, or the best possible substitute language if a canonical doesn’t exist for the same language.”

Setting the Canonicalized URL to ‘noindex’

Noindex and rel=canonical are completely separate tags and they should never be mixed even though they achieve similar objectives. By using both, Google will end up prioritizing your rel=canonical tags. In case you want to noindex and canonicalize any URL of your website, using a 301 redirect is recommended.

Frequently Asked Questions (FAQs)

Since canonical tags have not been widely used yet, there are many questions raised regarding these.

1. Is a canonical tag important? 

Canonical tags are important if you have the same or similar content posted on multiple pages. These tags help your website get indexed properly on Google and let the search engine know how to properly index your content in the search engine results pages.

2. What is the use of a canonical tag?

The purpose of a canonical tag is to help Google understand:

• Which version of a page needs to be indexed
• Which version of a page needs to be ranked for relevant queries
• If “link equity” is applicable for one page or it should be split between your content pages

3. How can I create a canonical URL?

Head to the Search Console homepage for your website:

• Click on the version of your content you want to make canonical
• Click on the gear icon and then click on Site Settings
• In the preferred domain settings, choose the version of the content you want to make canonical

4. Where should I place canonical tags?

The canonical tag should always be used as a page-level meta tag. You should place the canonical tags for your content in the HTML header for your webpages. Doing so automatically tells the search engine that it is the canonical version of the page.

5. Do canonical tags impact SEO?

Yes. There are two ways that canonical tags impact SEO. First, they can influence how search results are displayed, and secondly, they influence the general rankings of your websites based on how you structure your content. Since PageRank flow is affected by canonical tags, your website’s SEO is directly affected by the use of the tags.


The canonical tag is a powerful tool to resolve duplicate content issues. By identifying which pages should receive higher domain authority, you will be able to use the canonical tags on the right pages. However, the key is to use canonical tags effectively. If you overuse or misuse canonical tags, Google will stop taking your tags seriously and it will do more harm to your website than good. Hopefully, the guide has helped you understand the importance of canonical tags and why you should be using them to boost your SEO.

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