What Is a Canonical Tag? rel=canonical Explained

Search engines experience the content of a website differently from people. To a search engine every unique URL is a separate page. If a single page on your site can be reached through more than one URL with the same or similar content, Google reads those as duplicate versions of the same page. It will then pick one URL as the original and most important copy of that content and index it. Sometimes it gets that choice wrong and picks the wrong one. That is what we use the canonical tag for: to state which page is the right one.

Canonical Test Tool

Note: enter the full URL you want to test. For example: https://example.com/example/example.html

What Does the Canonical Tag Mean? An Example

The canonical tag is a piece of HTML that identifies the main version among duplicate or similar pages. It looks like this:

<link rel=”canonical” href=”/canonical” />

In that snippet the main version of the page is the part in “href =/canonical”.

Note: the canonical tag should only be used for URLs that are identical or nearly identical. It is not for grouping pages by topic.

Say you have a page titled “Canonical Page 2” and you consider the main page, “Canonical”, to be the right one. You need to place the code above in the content of BOTH “Canonical Page 2” and “Canonical”. If you have a third page, it too must carry the canonical tag pointing at the correct page.

The canonical tag was introduced by the major search engines in 2009 as a way for webmasters to resolve duplicate content problems and to preserve link equity and rankings by stating which version should be indexed in search results. The subject falls under technical SEO. 

How the Canonical Tag Affects SEO

Canonical is good for SEO because it helps Google understand duplicate content and cuts down the risk of it choosing the wrong URL as the canonical version. With a canonical tag in place, Google can consolidate link equity correctly, index the main version of your content and rank it for the relevant queries. 

Canonical: the Points That Matter

A few pieces of advice to take into account at the start:

• Use the URL Inspection tool in Google Search Console to see which page Google treats as the canonical version.
• When you are deciding between a redirect and a canonical tag, prefer the redirect unless it would hurt the user experience in some way.
• When you choose which page the canonical tag should point at, pick the version you consider the most important. The right page is usually the URL with the most links and the most traffic.
• The canonical tag should only be used for URLs that are identical or nearly identical. It is not for grouping pages by topic.