The canonical tag should be placed in the head section of the HTML document and should refer to the preferred version of a page. It should look like this:
<link rel="canonical" href="https://example.com/preferred-page.html">
href attribute should contain the URL of the preferred version of the page. By using the canonical tag, you are telling search engines that you want a specific page to be considered the authoritative version for a given set of similar pages. This helps to avoid duplicated content issues and ensures that the right page is displayed in search results.