What is canonical?
When professional SEO practitioners talk about "canonical", they are referring to an HTML markup element in the source code of a page. A canonical tag looks like this:
<link rel="canonical" href="https://www.google.dk/" />
This tag tells search engines that the page in question is a copy or variant of another page that the tag points to. Canonical tags are particularly useful on pages that function as variants of a "master page", such as sorting and filtering pages on webshops. When implemented correctly, you can avoid issues with duplicate content and thin content, and any incoming link value will be passed to the page the canonical tag refers to.
How do you create canonical tags?
Most common shop systems allow you to create canonical tags via the backend system. Some systems handle the markup automatically, while others require manual setup on each individual page. In some cases, it may be necessary to insert canonical tags directly into the website's template files. If you are not technically savvy, it may be necessary to contact a professional developer for assistance.
Which pages should use canonical tags?
Canonical tags should be used on pages that have nearly identical content to another page. A typical example is filtering and sorting pages in webshops. For example, a URL such as
https://webshop-eksempel.dk/kategori/sko/?filterparameter1=værdiY&sorteringsparameter1=Z
should have a canonical tag pointing to the primary category URL:
https://webshop-eksempel.dk/kategori/sko/
This signals to Google that the sorting and filtering page is merely a variant of the primary page, which prevents duplicate content and ensures that link value is consolidated on the primary URL.
Self-referencing canonical tags and dynamic pages
To avoid duplicate content issues, it is a good idea to include self-referencing canonical tags on all pages. This ensures that search engines know which version of the page should be prioritised, even when there is no direct duplicate content.
On dynamic pages such as filtering and sorting pages, canonical tags can consolidate signals from different URLs to a primary page. This helps prevent the dilution of link value and strengthens SEO on the correct URL.
Tools such as Google Search Console or third-party SEO tools can help identify duplicate content and verify that canonical tags are set up correctly.
Do you have duplicate content issues on your website?
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