rel=canonical: the ultimate guide

A canonical URL lets you tell search engines that certain similar URLs are actually the same. Sometimes you have products or content that can be found on multiple URLs — or even multiple websites, but by using canonical URLs (HTML link tags with the attribute rel=canonical), you can have these on your site without harming your rankings.

The rel=canonical element, often called the “canonical link”, is an HTML element that helps webmasters prevent duplicate content issues. It does this by specifying the “canonical URL”, the “preferred” version of a web page – the original source, even. Using it well improves a site’s SEO.

The idea is simple: if you have several similar versions of the same content, you pick one “canonical” version and point the search engines at it. This solves the duplicate content problem where search engines don’t know which version of the content to show in their results. This article takes you through how and when to use them, and how to avoid common mistakes.

The SEO benefit of rel=canonical

Choosing a proper canonical URL for every set of similar URLs improves the SEO of your site. This is because the search engine knows which version is canonical, so it can count all the links pointing at all the different versions as links to the canonical version. Setting a canonical is similar in concept to a 301 redirect, only without actually redirecting.

History of rel=canonical

In February 2009 Google, Bing and Yahoo! introduced the canonical link element – if you want to learn about its history, Matt Cutts’ post gives the clearest explanation. While the idea is simple, the specifics of how to use it are often complex.

The process of canonicalization

Ironic side note

The term Canonical comes from from the Roman Catholic tradition, where a list of sacred books was created and accepted as genuine and named the canonical Gospels of the New Testament. The irony is it took the Roman Catholic church about 300 years and numerous fights to come up with the canonical list, and they eventually chose four versions of the same story…

When you have several choices for a product’s URL, canonicalization is the process of picking one of them. In many cases, it’ll be obvious: one URL will be a better choice than others. In some cases, it might not be as obvious, but even then it’s still pretty simple: just pick one! Not canonicalizing your URLs is always worse than canonicalizing your URLs.

How to set canonical URLs

A correct example of using rel=canonical

Let’s assume you have two versions of the same page, each with exactly – 100% – the same content. The only difference is that they’re in separate sections of your site and because of that the background color and the active menu item are different – that’s it. Both versions have been linked to from other sites, so the content itself is clearly valuable. So which version should search engines show in results?

For example, these could be their URLs:

  • https://example.com/wordpress/seo-plugin/
  • https://example.com/wordpress/plugins/seo/

This is what rel=canonical was invented for and, unfortunately, this happens fairly often, especially in a lot of e-commerce systems. A product can have several different URLs depending on how you got there. In this case you would apply rel=canonical as follows:

  1. Pick one of your two pages as the canonical version. This should be the version you think is the most important. If you don’t care, pick the one with the most links or visitors, and if all else is equal, flip a coin. You just need to choose.
  2. Add a rel=canonical link from the non-canonical page to the canonical one. So if we picked the shortest URL as our canonical URL, the other URL would link to the shortest URL in the <head> section of the page – like this:
    <link rel="canonical" href="https://example.com/wordpress/seo-plugin/" />

    That’s it. Nothing more, nothing less.

What this does is “merge” the two pages into one from a search engine’s perspective. It’s a “soft redirect”, without redirecting the user. Links to both URLs now count as the single, canonical version of the URL.

Setting the canonical URL in Yoast SEO

Our Yoast SEO WordPress plugin lets you change the canonical URL of several page types in the plugin settings. You only need to do this if you want to change the canonical to something different from the current page’s URL. Yoast SEO already renders the correct canonical URL for almost any page type in a WordPress install.

For posts, pages, and custom post types, you can edit the canonical URL in the advanced tab of the Yoast SEO metabox:

Setting a canonical URL in Yoast SEO

For categories, tags and other taxonomy terms, you can change the canonical URL in the same place in the Yoast SEO metabox too. If you have other advanced use cases, you can also use the wpseo_canonical filter to change the Yoast SEO output.

When should you use canonical URLs?

301 redirect or canonical?

If you are unsure whether to do a 301 redirect or set a canonical, what should you do? The answer is simple: you should always do a redirect, unless there are technical reasons not to. If you can’t redirect because that would harm the user experience or be otherwise problematic, then set a canonical URL.

Should a page have a self-referencing canonical URL?

In the example above, we link the non-canonical page to the canonical version. But should a page set a rel=canonical for itself? This question is a much-debated topic amongst SEOs. At Yoast, we strongly recommend having a canonical link element on every page and Google has confirmed that’s best. That’s because most CMS’s will allow URL parameters without changing the content. So all of these URLs would show the same content:

  • https://example.com/wordpress/seo-plugin/
  • https://example.com/wordpress/seo-plugin/?isnt=it-awesome
  • https://example.com/wordpress/seo-plugin/?cmpgn=twitter
  • https://example.com/wordpress/seo-plugin/?cmpgn=facebook

The issue is that if you don’t have a self-referencing canonical on the page that points to the cleanest version of the URL, you risk being hit by this. If you don’t do it yourself, someone else could do it to you and cause a duplicate content issue, so adding a self-referencing canonical to URLs across your site is a good “defensive” SEO move. Luckily, our Yoast SEO plugin does this for you.

Cross-domain canonical URLs

Perhaps you have the same piece of content on several domains. There are sites or blogs that republish articles from other websites on their own, as they feel the content is relevant for their users. In the past, we had websites republishing articles from Yoast.com as well (with express permission), but if you had looked at the HTML of every one of those articles you’d found a rel=canonical link pointing right back to our original article. This means all the links pointing to their version of the article count towards the ranking of our canonical version. They get to use our content to please their audience, and we get a clear benefit from it too. Everybody wins.

Faulty canonical URLs: common issues

There are many examples out there of how a wrong rel=canonical implementation can lead to huge issues. I’ve seen several sites where the canonical on their homepage was pointed at an article, only to see their home page disappear from search results. There are other things you should never do with rel=canonical. Here are the most important:

    • Don’t canonicalize a paginated archive to page 1. The rel=canonical on page 2 should point to page 2. If you point it to page 1, search engines will actually not index the links on those deeper archive pages…
    • Make them 100% specific. For various reasons, many sites use protocol-relative links, meaning they leave the http / https bit from their URLs. Don’t do this for your canonicals. You have a preference, so show it.
    • Base your canonical on the request URL. If you use variables like the domain or request URL used to access the current page while generating your canonical, you’re doing it wrong. Your content should be aware of its own URLs. Otherwise, you could still have the same piece of content on – for instance – example.com and www.example.com and have each of them canonicalize to themselves.

      Multiple rel=canonical links on a page causing havoc. When we encounter this in WordPress plugins, we try to reach out to the developer doing it and teach them not to, but it still happens. And when it does, the results are wholly unpredictable.

      rel=canonical and social networks

      Facebook and Twitter honor rel=canonical too, and this might lead to weird situations. If you share a URL on Facebook that has a canonical pointing elsewhere, Facebook will share the details from the canonical URL. In fact, if you add a ‘like’ button on a page that has a canonical pointing elsewhere, it will show the like count for the canonical URL, not for the current URL. Twitter works in the same way.

      Advanced uses of rel=canonical

      Google also supports a canonical link HTTP header. The header looks like this:

      Link: <https://www.example.com/white-paper.pdf>;    rel="canonical" 

      Canonical link HTTP headers can be very useful when canonicalizing files like PDFs, so it’s good to know that the option exists.

      Using rel=canonical on not so similar pages

      While I wouldn’t recommend this, you can definitely use rel=canonical very aggressively. Google honors it to an almost ridiculous extent, where you can canonicalize a very different piece of content to another piece of content. However, if Google catches you doing this, it will stop trusting your site’s canonicals and thus cause you more harm…

      Using rel=canonical in combination with hreflang

      We also talk about canonical in our ultimate guide to hreflang. That’s because it’s very important that when you use hreflang, each language’s canonical points to itself. Make sure that you understand how to use canonical well when you’re implementing hreflang, as otherwise you might kill your entire hreflang implementation.

      Conclusion: rel=canonical is a power tool

      Rel=canonical is a powerful tool in an SEO’s toolbox, but like any power tool, you should use it wisely as it’s easy to cut yourself. For larger sites, the process of canonicalization can be very important and lead to major SEO improvements.

      Read more: WordPress SEO: The definitive guide to higher rankings for WordPress sites »

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19 Responses to rel=canonical: the ultimate guide

  1. anisa97
    anisa97  • 9 months ago

    I want to make rel canonical at http://driver-canon.com but i did not know how to do that?

  2. Justin P Lambert
    Justin P Lambert  • 9 months ago

    Sorry is this is a dumb question, but… If I’m creating several pages that all contain essentially the same content, but that are designed to appeal to different target searchers (headlines, images, a small number of changes in the text) would this be a good use of rel=canonical so the pages are not viewed as duplicate content? Or should I work on adjusting the wording of the content sufficiently that the search engines will not recognize them as dupes?

    • kamal
      kamal  • 9 months ago

      According to the guide above , yes you can.

  3. Gina
    Gina  • 9 months ago

    Hi there, if I have two similar pages where (for instance) the desktop optimized home page redirects to a mobile version specifically designed for small screens, which would be the best one to make canonical, the desktop or mobile url? The desktop version will have a bit more info and images.

  4. Karie
    Karie  • 9 months ago

    Hi, so I’m using the Yoast premium plugin (3rd year, it’s great) and I’m trying to figure out how to overcome duplicate meta for my blog archive pages. I thought the canonical would do the trick but now I’ve read it shouldn’t. Does it matter if it has duplicate meta (not sure if you can add different meta to each archive page) if the blog posts on it are all different? (I use excerpts on my blog page)
    Many thanks, I’m very green when it comes to SEO and your blog has helped me no end! Happy New Year to you!

  5. Kevin Pauls
    Kevin Pauls  • 9 months ago

    Well written. Rel=canonical is definitely useful and Google seems to like having things pointed out to them to make crawling and indexing easier but as you say, it can be over used.

  6. Nico Watts
    Nico Watts  • 9 months ago

    where has this website been all my life? i have learned so many important things today. i will keep reading. thank you YOAST

    • Willemien Hallebeek
      Willemien Hallebeek  • 9 months ago

      You’re welcome, Nico. Happy reading!

  7. Roberto Dainel
    Roberto Dainel  • 9 months ago

    Great information on rel=canonical. It is really very best option to get rid of duplicate pages.

    Thank You

  8. SEO Tips
    SEO Tips  • 9 months ago

    All these tips are handy for me. I m going to follow these SEO strategies with my business blog. This tactics are really great for growing business. Thanks a lot for creating this kind of beneficial contents.

  9. republic
    republic  • 9 months ago

    hi its really good to know about the canonical URL’s and its effect on a websites
    thank you for the information and by tips that you gave i have changed our site just have a look at and give your feed back

  10. Subodh Kumar Srivastava
    Subodh Kumar Srivastava  • 9 months ago

    We can use canonical tag on all page in website ? please suggest me … i Have 25+ page in my website

    • Willemien Hallebeek
      Willemien Hallebeek  • 9 months ago

      Hi Subodh, Yes you can! Just check out the heading “when you should use canonical URLs” above :-)

  11. NITIN MISHRA
    NITIN MISHRA  • 9 months ago

    you help me alot thanx yoast seo ,i am big fan of yours great service its very easy

  12. Catherine
    Catherine  • 9 months ago

    Canonicalization helps the most with SEO, it definitely is a power tool when it comes to an e-commerce site with various product pages using various filter options.

    • Willemien Hallebeek
      Willemien Hallebeek  • 9 months ago

      It is! Thanks for your comment, Catherine.

  13. JANI BABU ANSARI
    JANI BABU ANSARI  • 9 months ago

    I have a question, Can I use the canonical link in a single post to encourage search engine bots to index our post fastly.

    • Willemien Hallebeek
      Willemien Hallebeek  • 9 months ago

      Hi Jani, Not sure what you mean. Do you mean a self-referencing canonical URL?

  14. Crest Family Dental
    Crest Family Dental  • 9 months ago

    Awesome blog. Very useful information, it clarified a lot of things to us. Thanks for sharing your views.- dentist in hartford ct