SEO: Canonical Tags
Canonical tags are an HTML element used to help prevent the problem of duplicate content by specifying “preferred” versions of a web-page. This is a useful tool in effective search engine optimization, especially for larger portals and shops that often have problems with duplicate content or similar content (near DC). Duplicate content occurs when, under different URLs, the same or almost the same content is provided. This is a particular problem for online shops that use filters for sorting products. An widely accepted solution to these technical challenges is the so-called canonical tag, or canonical attribute as it is also known.
How Canonical Tags Work
If multiple URLs deliver the same or very similar content, the preferred URL is specified in the header by canonical attribute as seen below:
One of the major benefits of the canonical attribute is that the links and their effects, as well as the PageRank which refer to the non-preferred URLs, are passed to the preferred URL. It is therefore strongly advised for websites, especially those featuring product filters, implement canonical tags.
Canonical tags for International Domains
Many modern businesses offer their online content, their products and their services in a variety of different languages. A majority of these enterprises publish their content on their own, country specific toplevel domains, for example: yourbusiness.co.uk for the United Kingdom or yourbusiness.de for Germany. In principle, these domains are extremely advantageous.
However, it is much simpler for the user to be directed to the right version immediately via a language switch in order to lead those who simply type “yourbusiness.com” in the browser directly to the right domain.
In order to do this, the rel=”alternate” hreflang= “x” tag is used to tell Google that a website has several versions in other languages. To this end, international businesses are advised to add each of their language versions in the tag on each page. The country as well as the language can be indicated in the hreflang. By doing this, businesses can also allocate countries with several languages correctly. The rel=”alternate” hreflang= “x” tag should be used as follows: This will link German speaking users living in Germany to the German version of the website.