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What is Canonical Tag in SEO – A Complete Guide

What is Canonical Tag in SEO

If your website has multiple pages with similar content (for instance, a page with desktop and mobile versions), or a single webpage accessible by different URLs – Google considers the content as duplicate versions of the original page. Hence, the search engine will mark only one URL as a canonical (primary) version and crawl only that page. It considers all other pages as duplicates and these are less likely to be crawled by Google bot.      

This can significantly impact your search engine results unless you precisely indicate which URL is canonical. Using canonical tags (“rel canonical”) helps specify that a particular URL is the master copy of the page. This can prevent problems arising from duplicate or identical content that appears on multiple URLs. To put it simply, canonical tags indicate which version of the page (URL) you want search engines to crawl and index for Search Engine Result Pages (SERPs).

In this blog, we will discuss what is a canonical tag in SEO and how you can benefit from it.

What is a Canonical Tag?

It is a small piece of HTML code that helps Google choose the right canonical URL, i.e., the “primary” version of the page from other similar or identical URLs. In terms of Search Engine Optimisation, a canonical tag lets Google understand which version of the page or content you want to appear in search engine results. This can help you get link equity from all duplicate pages and also ensure better crawling and indexability of the website. Here’s how Google describes what is Canonical URL:

Why Use a Canonical URL for SEO?

Canonical tags play an integral role in search engine optimization. Let’s check out here:

  • To help Google understand which URL you want your target audiences to see in search engine results. In absence of a canonical tag, Google will crawl and index only the page that “it” thinks is the original version. Adding canonical tags linking to canonical URLs indicates to Google which pages to ignore and which to crawl.
  • Using canonical tags helps Google to consolidate all the information (including links) from individual URLs into one preferred URL. That means links coming from other sites to duplicate pages will get consolidated with links to the “main” page – enabling you to make the most of the link juice.
  • Canonicalization is an effective tool to manage your syndicated content on other domains. This will help ensure the preferred URL shows up in search engine results.
  • Too much duplicate or similar content on your website can significantly affect the crawl budget. That means Google will waste more time crawling & indexing multiple versions of the same URL rather than finding more crucial content on the site. By using canonical tags, you will prevent Google from wasting time crawling & indexing duplicate content, thus, keeping the crawl budget under control.   
  • Canonicalization also helps streamline tracking metrics for a particular piece of content, topic, or product.

How Google Reads and Crawls Canonical URLs?

There are different factors based on which Google reads and crawls canonical URLs. These may be:

  • Whether the page URL is served by “http” or “https”
  • Presence of the URL in your sitemap
  • Page quality
  • Any type of “rel=canonical” labelling

Using these techniques, you can indicate the preferred URL of the main version of the page to Google. However, due to various reasons, the search engine may still pick a different URL as canonical than what you tag.

For example, if a single page has different language versions, Google may consider them as duplicates in case the primary content is in the same language. This means, if only the non-critical part of the text, the header and the footer are translated into other languages and the content body remains the same, Google will consider it a duplicate despite canonical tags. So, if you are wondering how Google considers a page as canonical, remember that it will typically point to the page marked as canonical. However, if one of the duplicate pages explicitly meets the search query in terms of quality and content, Google will crawl and rank it in search results. For instance, if a user is browsing on a mobile device, Google is likely to point to the mobile version of the page even if the desktop version is marked as canonical.

Canonical Tag Best Practices

Using canonical tags is pretty straightforward. Here are some proven practices to follow to use canonical tags for SEO.

1. Always Use Absolute URLs

As Google’s John Mueller suggests, avoid using relative paths when adding rel= “canonical” link element.

Therefore, it is preferable to use an absolute path in the following structure:

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

<link rel=“canonical” href=”/sample-page/” />

2. Include Self-Referencing Canonical Tags

Add canonical tags on an URL or page referencing itself even if the canonical tags are not present on duplicate pages. When you use self-referencing rel=canonical on the original or main page, it gives a clear signal to Google that it is a canonical version.

3. Add Canonical Tags to Cross-Domain Duplicate Pages

Canonicalize does not just primary pages from your website but also pages from other domains. In case there is duplicate content on pages on different websites, follow the below strategies:

  • Apply canonical tags even on external pages, pointing to the original page
  • Use self-referencing canonical tags on the original page

4. Use Lowercase URLs

Google search engine is pretty sensitive about lower cases and upper cases used in the URLs. However, as an SEO best practice regarding canonicalization, use lower cases in your canonical URL. This will help avoid duplication problems and maintain consistency in the eyes of Google. It is also recommended to use lowercase in all URLs on your servers and use them for canonical tags as well.

5. Check the Dynamic Canonical Tags

Ensure bad coding isn’t causing a website to write multiple and different canonical tags for each version of the page. Eventually, the entire purpose of using canonical tags gets missed here. It is crucial to thoroughly check all your URLs, particularly in the case of CMS-driven and eCommerce sites.

6. Canonicalize the Home Page Proactively

Duplicating the homepage is most common among websites. Even people link to the homepage in different ways which are often beyond your control. Hence, it is important that you add a canonical tag on the home page template to avoid future problems.

The Final Words

It isn’t that complicated to understand what is a canonical tags in SEO and how to use them to improve your search engine results. However, it is important to understand that canonicals are only signals and not directives for search engines. Hence, Google may pick a different URL unlike what you declare as canonical.        

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