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While there are many copies of a page on your website, a canonical URL is the address of the original version of the page —the canonical presented in your HTML help to specify the canonical URL. With SEO canonical tags, Google can distinguish between the original page and its duplicate when crawling through pages.

When acknowledging SEO, learning about canonical URLs is highly necessary. Correct canonical URL implementation can improve your site’s ranking on Google and other search engines. Then, what are canonical tags? This article is a guide to optimizing this element in your SEO strategy or SEO audit service implementation.

What Are Canonical Tags? The Simple Guide For SEO Canonical Tags

What Is A Canonical Tag?

SEO canonicals (or rel=canonical) are part of the HTML code that assists search engines in distinguishing the original version of the website from other duplicate pages that are identical or substantially similar to it.

When enhancing SEO, canonical tagging informs Google of the selected version of the page that will appear in search results. Moreover, it combines link equity from duplicate pages and enhances your website’s crawling and indexing.

Read more: What is duplicate content?

What Is A Canonical Tag?

What Does A Canonical Tag Looks Like?

Canonical tagging is designed with simple and consistent syntax and put in the middle of the <head> section of a web page:

<link rel=“canonical” href=“https://example.com/sample-page/” />

Look complex, right? But here is the simplification of the canonical tag definition:

  • link rel=“canonical”: The link in this tag is this page’s main (canonical) version.
  • href=“https://example.com/sample-page/”: The canonical version presents at this URL.
What Does A Canonical Tag Looks Like?

Why Does Canonicalization Matter in SEO?

Duplicate content is not acceptable to Google. It makes it more difficult for them to decide:

  • The index page
  • The page rank for related queries
  • Whether they should combine “link equity” on a single page or distribute it over many versions.

Moreover, your “crawl budget” may also impact if there is too much duplicate content. As a result, Google can spend time indexing numerous copies of the same page rather than finding other valuable information on your website.

Canonical rel address each of these problems. They let you instruct Google on which page version to index, rank, and consolidate any “link equity.”

6 Canonical Tag Best Practices

There are five recognized methods for defining canonical URLs. The six examples of SEO canonicalization are:

  1. SEO canonical tags can self-refer to other tags
  2. Activate SEO canonicalization for your homepage
  3. Verify your dynamic SEO canonicals precisely
  4. Maintain clear signals
  5. Use caution while canonicalizing near-duplicates
  6. Canonicalize cross-domain duplicates
6 Canonical Tag Best Practices

SEO canonical tags can self-refer to other tags

A canonical tagging may reference the current URL without issue. In other words, it is acceptable to place the tag corresponding to URL X on URL X if URLs X, Y, and Z are duplicates and X is the canonical version. While it may seem straightforward, there must be more understanding around this.

Activate SEO canonicalization for your homepage

It is reasonable to include canonical URL SEO in your homepage template to avoid unanticipated issues. This situation happens when that homepage duplicated versions are relatively prevalent, and people may link to your homepage in numerous ways.

Activate SEO canonicalization for your homepage

Verify your dynamic SEO canonicals precisely

A website may occasionally create a different canonical tagging for each URL version due to improper programming. Therefore, verifying your URLs, particularly on e-commerce and CMS-powered websites, is necessary.

Maintain clear signals

Search engines can ignore or misinterpret a canonical tag if you transmit conflicting signals. In other words, avoid canonicalizing page A to page B and subsequently page B to page A. Furthermore, do not 301 redirect page B to page A after canonicalizing page A to page B.

Moreover, canonical chains  (A—>B, B—>C, C—>D) are typically not recommended if at all possible. Give clear signals to avoid driving search engines to operate poorly.

Maintain clear signals

Be cautious while canonicalizing near-duplicates

The majority of people identify SEO canonicalization as exact duplication. Using canonical URL SEO on sites with almost identical content (near duplicates) is possible, but it is still better to be cautious. Although there is much discussion on this subject, it is typically acceptable to use SEO canonicalization for similar sites, such as product pages that only differ in currency, location, or a single product attribute.

Remember, non-canonical versions of a page might not rank, and if the pages are too distinctive, search engines might ignore the tag.

Canonicalize cross-domain duplicates

The canonical tag definition shows that you may use it across domains if you are the site owner of both. Imagine you work for a publishing business that frequently distributes the same article over six different websites. With SEO canonicalization, you may concentrate your ranking strength on a single site. Remember that canonicalization will prohibit non-canonical sites from ranking, so double-check that this use supports your business case.

Canonicalize cross-domain duplicates

What to Avoid with Common Canonicalization Mistakes?

The subject of SEO canonicalization is challenging. As a result, many things need to clarify regarding how to canonicalize correctly.

These are several errors that people frequently make while trying to canonicalize:

  1. Using robots.txt to prevent access to the canonicalized URL
  2. Changing the canonical URL to ‘no-index’
  3. Updating the canonicalized URL’s HTTP status code to 4XX
  4. Canonicalizing every page with pagination to the main page
  5. Using hreflang without SEO canonicals
  6. Having several rel=canonical tags rel=canonical
  7. Placing rel=canonical in the <body>

Using robots.txt to prevent access to the canonicalized URL

When you block a URL in robots.txt, Google stops indexing it, which means they can’t see any SEO canonical tags on that page. As a result, they can not convert any “link equity” from the non-canonical to the canonical.

Using robots.txt to prevent access to the canonicalized URL

Changing the canonical URL to ‘no-index’

Never combine rel=canonical and no-index. These are incompatible instructions.

Google often precedes canonical tagging over the “no-index” tag. But this is not a reasonable idea. Instead, use a 301 redirect to no-index and canonicalize a URL or rel=canonical.

Changing the canonical URL to 'no-index'

Updating the canonicalized URL’s HTTP status code to 4XX

Updating the URL’s HTTP status code to 4XX will cause the same consequences as the “no-index” tag, which prevents Google from observing the SEO canonicalization and changing “link equity” to the canonical copy.

Canonicalizing every page with pagination to the main page

No canonicalized pagination should direct to the first page in the series. Instead, canonicalize every page with pagination to the main page.

For pagination, you also need to utilize the rel=prev/next tags. FIY, Google no longer makes use of them, but Bing does.

Using hreflang without canonical tagging

Hreflang tags indicate a website’s language and geographic targeting.

When utilizing hreflang, Google advises that you specify canonical URL SEO in the same language or the best available alternative language if a canonical doesn’t exist for the same language.

Using hreflang without canonical tagging

Having several rel=canonical tags 

Google may overlook tags with multiple rel=canonical attributes. This case frequently occurs due to the system’s several sites of tag insertion, including the CMS, the theme, and the plugin (s). For this reason, many plugins contain an overwrite feature that ensures they are the sole source of SEO canonical tags.

Canonicals inserted using JavaScript are another instance where this may be a problem. When adding the rel=canonical element using JavaScript, if no canonical URL is available in the HTML response, it should be recognized when Google displays the page. Nevertheless, if you specify a canonical in HTML and then replace the preferred version using JavaScript, you give Google conflicting information.

Placing rel=canonical in the <body>

Only the document’s head> should have the rel= “canonical” attribute. A page’s body part will not consider SEO canonicals.

This case might cause issues while parsing a document. While the rel=canonical tag may be present in the right spot, many factors, such as unclosed tags, JavaScript injected, or iframes> in the head> section, might cause the head> to terminate when rendering. In certain circumstances, canonical tagging can inadvertently find its way into the rendered page’s body>, where it does not need to involve.

How to Find and Fix Canonicalization Problems?

Canonicalization is prone to errors. Thus it pays to routinely check your website for problems with canonical tags and address them as soon as possible. An SEO audit service searches your website to check for over 100 SEO problems, including canonical rel issues.

Here are the common problems with canonical URL SEO that Site Audit could uncover and solutions.

How to Find and Fix Canonicalization Problems?

Canonical references 4XX

This warning results from canonicalizing one or more pages to a 4XX URL.

Reason:

When 4XX pages do not function, search engines will not index them. Thus, they will disregard any canonical taggings referring to these pages and frequently index the page’s incorrect (non-canonical) version.

Solution:

Examine the impacted pages and replace any dead (4XX) canonical links with active (200) pages you want to index.

Canonical references 4XX

Canonical references 5XX

This warning appears when one or more pages are canonicalized to a 5XX URL.

Reason:

5XX HTTP status codes denote server problems that make the canonical page unavailable. Google may disregard the canonical since it is unlikely to index unavailable pages.

Solution:

Replace all incorrect canonical URLs with accurate ones. If the given canonical appears correct, look for server configuration errors. Remember that if the crawl happened when your site was out for maintenance or the server was overloaded, this could be a temporary problem.

Canonical references 5XX

Canonical refers to redirect

This alert appears when one or more pages are canonicalized to a redirected URL.

Reason:

Canonicals should refer to a page’s most recent authoritative revision. Redirecting url is an exception to this. Search engines need to understand or respect the canonical.

Solution:

Replace canonical links with direct links to the most authoritative version of the page (one that receives a 200 HTTP status code without redirecting).

Canonical refers to redirect

Related post: How to improve page speed?

Pages that are duplicated without being canonical

This warning appears when one or more pages are identical or highly similar but don’t identify a canonical version.

Reason:

Because no canonical is mentioned, Google will attempt to find the most relevant version to present in search results. You should avoid indexing this version.

Solution:

Examine the duplicate groupings. Choose one version for indexing in the search results to use as the canonical version. Set this as the canonical chains for all copies (and add self-referencing SEO canonical to the canonical version).

Hreflang to non-canonical 

This error appears when one or more pages have a non-canonical URL in their hreflang annotations.

Reason:

It is best practice for hreflang links to always go to the canonical pages. Search engine confusion and misdirection can result from links to non-canonical versions of pages in hreflang annotations.

Solution:

Change any links to their canonical versions in the hreflang annotations of impacted pages.

Hreflang to non-canonical 

No internal inbound links exist in the Canonical URL

This error appears when none of the given canonical URLs have internal inbound links.

Reason:

Canonical URLs are invisible to website visitors without internal connections. Instead, users are being directed to a non-canonical version of the page somewhere on the website.

Solution:

Link directly to the canonical wherever there are internal references to canonicalized pages.

Organic traffic goes to non-canonical pages

This warning appears when one or more non-canonical sites receive organic search traffic, which is something that shouldn’t happen.

Reason:

Google may have ignored the given canonical tags, or your canonical tags are misconfigured.

Solution:

Verify that all reported pages have rel=canonical tags appropriately configured. If that is not the problem, check Google Search Console’s URL Inspection tool to verify if they see the supplied canonical URL as canonical. If there is a discrepancy, look into the potential causes.

HTTP to HTTPS conversion rule

This warning appears when one or more non-secure (HTTP) pages designate a secure (HTTPS) version as canonical.

Reason:

The HTTPS protocol is preferred over HTTP. It makes no sense to designate the HTTPS version of a page as the canonical version when the HTTP version already exists.

Solution:

Apply a 301 redirect from HTTP to HTTPS. A direct link to the page’s HTTPS version is better than internal links pointing to the HTTP version.

HTTP to HTTPS conversion rule

HTTP to HTTPS conversion rule

This warning appears when one or more secure (HTTPS) pages designate a non-secure (HTTP) version as the canonical one.

Reason:

Assigning secure versions of pages as canonical wherever feasible is more appropriate because HTTPS is a ranking factor.

Solution:

Transfer the HTTP page to its HTTPS counterpart. If it is not feasible, link the HTTP version of the page to the HTTPS version using rel=”canonical” instead.

Unable to match canonical Open Graph URL

This warning appears when the given canonical URL and the Open Graph URL on one or more pages do not match.

Reason:

Social networks will distribute a non-canonical version of a website if the Open Graph URL does not match the canonical.

Solution:

Replace the Open Graph URL with the canonical URL for impacted sites. Verify that the two URLs match.

Unable to match canonical Open Graph URL

Frequently Asked Questions

How to use Canonical tags properly?

Canonical tag definition is simple. You should always keep in mind these five golden guidelines to use canonical rel properly, regardless of the approach you choose:

  • Use absolute URLs
  • Use lowercase URLs
  • Use the correct domain version (HTTPS vs. HTTP)
  • Use self-referential SEO canonicals
  • Use one canonical tag per page

What is a canonical link?

A canonical link informs search engines that a particular URL represents the master copy of a resource. Using the canonical rel, you can prevent problems caused by the same or “duplicate” content appearing on various URLs.

What is a canonical link?

How to check if a page is canonical?

  1. Right-click on your website to see the page source.
  2. With Ctrl F, look up “canonical.”
  3. Verify that the URL of the page you want to be indexed is in the href= element of the link.

Conclusion

What are SEO canonical tags? Out of a thousand websites, it is easy to find a duplicated webpage that contains similar content as yours. Therefore, making your page distinguishable from duplicated pages is the purpose of canonical chains. With the help of canonical tags, search engine like Google can easily crawl your page, which improves its visibility. 

This is the guide to canonical tag definition. In short, canonical chains are relatively easy to use. Said they take some time to understand. But remember that SEO canonicalization is a signal to search engines rather than a direction. In other words, they could decide on a canonical difference from the one you proclaim.