Specifying canonical tags is one of the most basic search engine optimisation actions you can take for your online shop. In the source code of a website, canonical tags specify which URL should be prioritised by search engines. Duplicate content can thus be avoided, even with the same content on different URLs.
Each unique piece of content on a website should only be accessible at a single URL. Otherwise, duplicate content is indexed. This means that in order to answer a search query, a unique URL cannot be found by the search engine. This often leads to poorer rankings.
How can different URLs be created?
A source for different URLs on a web page can be the structure of shop software and content management systems. For example, in most Shop software systems, the URL path is often built according to the categories in which the articles are assigned. But most of the time, items are placed in several categories. For example, a green dress could be listed under the category "clothes" and also under "green".
It is the same product page but two URLs are generated. Here, you should now indicate with a canonical tag, which URL is to be used by the search engines to display the results.
In addition, URL variants can result from dynamic URLs or tracking parameters. Examples:
How are canonical tags specified?
Canonical tags are specified in the source code.
If the same content can be retrieved via several other URLs, you can specify for search engines as follows:
<Link rel = "canonical" href = "https://theshop.com/clothes/Green-dress / "/>
This element with the attribute rel = "canonical" must be added to the <head> section of these pages and all variants.
It should be given the absolute URL (with domain), not only the relative URL (which would contain “/dresses/green-dresses/”).
Most Shop software systems default to a canonical tag for the individual pages, or this can be set as an option. In the case of the various categories, some systems, such as OXID, can set a main category that is used for the URL path.
Here are more Shop software systems, which explain the settings for the canonical tags:
In this video, the function of canonical tags is explained further: