A “canonical tag” is an HTML element that is used to indicate the preferred or “canonical” version of a web page. It is a way for website owners to specify which URL should be considered the authoritative source for a particular piece of content, in cases where the same content is accessible via multiple URLs.
The canonical tag is added to the HTML header of a web page and is used to indicate the preferred URL to search engines and other web-based tools. For example, if a page is accessible via both www.example.com and example.com, the website owner could use a canonical tag to indicate that the preferred version of the page is www.example.com.
The use of canonical tags helps to prevent duplicate content issues and ensures that search engines are able to properly index and rank a website’s content. By using canonical tags, website owners can also improve the visibility and credibility of their site, as search engines are able to distinguish between the preferred and non-preferred versions of a page, and are able to associate all backlinks and social signals with the preferred URL.