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Home » WTF is a canonical tag?

A canonical tag is a link tag in which you tell the search engine spiders that the same content is on yet another URL and that that URL is leading.

The canonical tag is recognized by all major search engines. It is a technical way to prevent duplicate content. This tag is placed in the <head> of your website and is ideally located on every page, even if the page is the only page with this content.

<link rel = “canonical” href = “” />


When do we use a canonical tag?

The canonical tag is most often used to prevent problems with filter pages (which we highlighted earlier in our 5 technical SEO tips for optimization), for example. If you have many of the same products in a webshop and your consumer can filter these by color or size for example, then the same products will be common but will still have the same URL.

Not all those URLs are relevant to the search engine results, because many products, after a period of time, become sold out or taken out of the collection. Suppose a website has the following two URLs:


A specific black shoe with sequins is sold on one URL. On the second URL the shoe is in size 42. The content of the second page is almost identical to the page on the first URL. The page with a size is not only in size 42, but also in 38, 40 and further. Because in this case each size has its own URL, duplicate content is created.

To tell search engine spiders which URL is the ‘main URL’, the canonical tag can be used, in this case the URL without size.

This is placed in the <head> of the page that cannot be indexed and refers to the main URL, the canonical page.

The canonical then looks like this: <link rel = “canonical” href = “” /> The canonical URL can be used between 2 domains.

If for any reason you publish content in another place, the canonical tag indicates which URL should be indexed. The canonical tag is a signal to a search engine spider, not a hard requirement. If you really want to avoid duplicate content, look for another technical solution like a meta robots tag “noindex, nofollow”, or a Disallow: in the robots.txt or 301 Permanent Redirect. The best solution differs per case.

Our consultant can advise you on this.

Learn more here about Canonical Tags:


Mathias Aaftink

Author Mathias Aaftink

Intrigued by customer behavior, online performance marketing and customer experience and the way organizations act on that. With my experience I feel comfortable in the world of (digital) marketing and branding. I take on new challenges with great pleasure and I immediately feel a great sense of responsibility for making it into a success. Projects where I can use my entrepreneurial skills and mindset give me a lot of energy and this is where I can be an added value for for you.

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