What is a canonical tag, and how is it used in SEO?

@elmo.conroy 

A canonical tag is an HTML element used in Search Engine Optimization (SEO) to indicate the preferred version of a webpage when it has multiple versions or similar content. It helps search engines identify and consolidate duplicate or similar content under a single URL, preventing issues related to duplicate content and potential SEO penalties.

When multiple URLs have identical or highly similar content, search engines may struggle to determine which one to index. In such cases, using the canonical tag informs search engines about the primary or preferred version of the content. This can be useful in situations like:

1. Duplicate content: If the same content exists on different URLs due to printer-friendly pages, sorting options, HTTP/HTTPS versions, or other reasons, using a canonical tag helps specify the original source or preferred version.
2. Similar content: When different pages have similar content but are not necessarily identical, using a canonical tag on one of the pages helps indicate the main version. This is commonly seen on e-commerce websites with similar product descriptions across multiple pages.

By including the canonical tag in the HTML code of a webpage, along with the appropriate URL reference, website owners can guide search engines to index the desired version and consolidate the ranking signals, ultimately helping to avoid content duplication issues in search engine rankings.