Canonical Tag: This is How You Protect Yourself From Duplicate Content

Canonicals help you fight duplicate content and rank the right content on Google. In my blog post, you will find out what the canonical tag is exactly, in which cases you should use it, how to do it and which common mistakes you should avoid.

What is a Canonical Tag?

Canonicals help you to control the ranking URL of your site. This is especially relevant if you have the same or very similar content on the website: The canonical tag is a link in the source code of a page. The duplicates link to the so-called canonical = representative URL and thus identifies this as the URL that you want to prefer in the index. The canonical URL also has a canonical: However, this refers to itself.

Incidentally, one does not speak of a canonical tag, but rather of a canonical link. However, the name Canonical Tag has become commonplace.

Why are there, canonicals?

Manfred Mandel is an online marketer at Magic-Mandel-Fantasie. Some time ago, he published a how-to article on his website. This article is available both as a magazine article and as a PDF. Every day he checks the search results to evaluate the success of this advice article.

On a Monday morning, he saw that instead of the magazine article, its print PDF was suddenly ranking! He has to answer to his CEO, who is not enthusiastic. After all, the targeted lead generation – a newsletter registration – is not possible with the PDF. Manfred should find a solution as soon as possible. The CEO wants to keep the PDF, but Manfred is not allowed to deindex it either. Desperate for a solution, he comes across the canonical attribute. That doesn’t sound bad at all …

Why are canonicals important to SEO?

Suppose there are several pages with the same or very similar content on your site. In that case, Google often cannot decide which content is the most relevant, for example, PDFs, print versions, and HTML pages or URLs with identical content with and without parameters. Instead of deciding on one page, Google then often indexes all versions, and you have duplicate content on Google in the index.

At the same time, none of these versions rank as well as a single “version” could if only they existed. In the worst case, it even goes as far as in the case of Manfred Mandel: Google has decided on content and ranks it in the top ranks – but not the one that you prefer. With the canonical tag, you can inform Google that there is a major version of this content and that it can and should index it. So the canonical is an important SEO tool.

Including the canonical tag

You integrate the canonical link into the head area of ​​the page for HTML documents. To avoid mistakes, Google recommends specifying the canonical URL as an absolute link rather than a relative. The original resource refers to itself, its copies and variants to the canonical URL.

<link rel = “canonical“ href = “ “ />

Broken down, the individual elements of the canonical say the following:

<link: Opens the link tag

rel = “canonical”: is the actual canonical attribute

href =” “: Is the link to the canonical URL

/ >: closes the link tag

Canonicals can also be integrated into PDFs and other non-HTML files. To do this, they have to be built into the http header and look like this:

Link: <>; rel = “canonical”

Common mistakes

In our analyzes, we keep seeing the same errors that occur when using canonicals. These are the most common:

The canonical URL cannot be reached.

Always make sure that the canonical URL is reachable. You can easily check this by checking the status codes of the canonical targets, for example, via a crawl with & Co.

Simultaneous use of rel = “canonical” & “noindex”

John Mueller from Google has confirmed it: the simultaneous use of canonicals and noindex is undesirable for the following reason: While the canonical says that two pages are identical, the “noindex” tag says that the page should not be indexed. Google then has to ask itself the following question: If this page shouldn’t be indexed, then neither should its original, right?

Canonicals on pagination pages

Don’t use canonicals on back pagination pages to refer to the first page. The pages are not identical; their content is different, so a canonical tag doesn’t make sense.

More than a canonical

Make sure you only have one canonical on each side. If you use several, Google will simply ignore all canonical links.

Canonical tag for different pages

Only use the canonical attribute if the pages are very similar. If you differ too much, Google will ignore your canonical instructions. To check whether Google accepts your canonical, you can use the “info:” search operator on Google. Enter the URL of the duplicate after the operator; the canonical URL should appear as a result:

Canonical link in <body> instead of <head>

The canonical should always be in the head area or the http header. If you’ve pasted it somewhere else, Google will ignore it.

301 redirect or canonical?

With the status code 301, you inform the search engines that the page has been moved permanently. Google only crawls the forwarding destination, not the originating page. The users are also taken directly to the new page. If you use Canonicals, Google will continue to crawl the duplicates, and the users can still access these pages.

Sometimes it is simply technical or not feasible for usability reasons to set a 301 redirect – then you can work with canonicals. Even if the content is presented in different formats, such as a print version and as a “normal” blog post, you can use canonicals instead of forwarding them. The canonical is only an indication for Google – which it usually follows, but which is not mandatory for Google. A 301 redirect, on the other hand, cannot be ignored by Google.

Canonical and hreflang

Hreflang and canonicals are closely related. If Google no longer accepts one of the two, you can ignore both instructions. So make sure that each country’s version has the canonical on its page. How you use canonicals and hreflang together, I also explained in my blog post about hreflang.

Conclusion: Canonicals are important!

When Manfred Mandel instructed the IT department to implement canonicals for the Magic Mandel Fantasie website and not to cut out the PDFs, it didn’t take long, and he was able to convey the good news to his CEO that his advisor was back -Article appears on Google in search results. For Manfred, one thing is certain: the research on canonicals has paid off.

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