Rel canonical tag
What is the rel canonical tag?
When a website has two versions of same content, the canonical (or re canonical) tag tells a search engine which version to index.
If a website has two pages (Page A and Page B) with duplicate content. You can use the canonical tag to tell the search engine which of the two pages to index.
What does it look like?
The canonical tag can be found in <HEAD> section of a webpage.
<link rel=”canonical” href=”http://www.example.co.uk” />
When should this tag be used?
You should always canonicalise your homepage to the version you want it to be known as e.g.
Often we create a web page which is later superseded by a page with better content and more informative. The canonical tag is the ideal tool for letting the search engines know which page(s) should be indexed.
Sometimes it is inevitable that you will have duplicate content on a website and deleting the page isn’t an option. A canonical tag can be used to tell the search engine to index the most up to date and useful page.
Depending on the nature of the content, you could also use a 301 direct.