A canonical tag is a way of telling search engines that a specific URL represents the unique copy of a page.
Using the canonical tag prevents problems caused by identical or duplicate content appearing on multiple URL s.
Basically, the canonical tag tells search engines which version of a URL you want to appear in Google search results.
The search engine friendly URL that you want the search engines to treat as authoritative. In other words, a canonical URL is the URL that you want visitors to see.
By applying a canonical tag:
<link rel=”canonical” href=”
https://www.sitename.com” />