Definition: The canonical tag is a link element in the header of a page. It informs search engines where the original content is located (i.e. the URL). Only this should be indexed by the search engine. Several versions are created, for example, on dynamic websites when content is filtered. As all pages have the same content, only one version should be indexed.
Content
Where do I insert the canonical tag?
What do canonical tags have to do with SEO?
What does Google say about using the canonical tag?
Where do I insert the canonical tag?
The canonical tag is only used in the head section of the website and not anywhere in the body. It is an attribute of the link element. You should include the tag on all pages that have the same or similar content to the original page "mypage.com/originalpage".
For example, you have a blog with the URL "mypage.com/blog". Your visitors can display this as a table, list or grid. This results in different URLs with different views but the same content:
www.meineseite.de/blog/tabelle
www.meineseite.de/blog/liste
www.meineseite.de/blog/rasterThe same applies to category pages of online stores: Depending on the search setting and filtering, several dynamic URLs are generated for the same content, e.g:
www.meineseite.de/shop?category=kleider
www.meineseite.de/shop?category=kleider?style=kurz
www.meineseite.de/shop?category=kleider?style=langSearch engines only want and should index one version, as multiple versions of identical content do not offer any added value. To use the canonical tag, enter it in the head of all version pages:
This signals that this URL is the original. As the canonical tag always refers to the original page of a piece of content, it is useful if the original page also refers to itself.
What do canonical tags have to do with SEO?
An important negative factor in SEO is duplicate content, i.e. the occurrence of the same or very similar content on a website. As described in the example above, it is sometimes necessary from a technical point of view to create several URLs for the same content. If you do this on your website (blog articles, store, etc.), we recommend using the canonical tag.
This also makes it easier to measure success. If several URL versions are indexed, there is also the possibility that your visitors reach your website via different URLs. In this case, the traffic to the page would be split. A single indexing would increase the relevance of this page for a keyword (consolidation).
Several indexable URLs can also be linked separately. In this case, your URLs would have to share the linkjuice. The canonical tag directs the linkjuice of all version copies to the original.
What does Google say about using the canonical tag?
Google has published a very informative article for webmasters. It also deals with other duplicate content problems with a technical background. An important piece of information from Google is that the canonical tag should point to the page that has the most content. This applies to pages with pagination: you have a lot of content that you want to distribute over several pages. Your visitors can navigate via page numbers or "forward" and "back". If you create a URL version that offers all content, e.g. 'mypage.com/blog?=viewall', then this would be the version with the most content.
