Canonical URL

When the same content exists at multiple URLs, the rel="canonical" link tag is used to tell the search engine, "this is the primary one."

Canonical URL (Canonical URL) is the URL that a search engine accepts as the “primary/representative” version of a web page. In cases where the same or very similar content exists at multiple URLs, it is specified with the <link rel="canonical" href="..."> tag.

Common cases where canonical should be used:

• HTTP and HTTPS versions existing at the same time
• WWW and non-WWW versions
• Sorting, filtering, and tracking parameters in the URL (utm_*, ?sort=)
• Serving mobile and desktop on separate URLs
• The same product being listed under different categories
• Printable versions (?print=1)
• Paginated listing pages

The canonical tag is not a directive, but a hint. Google makes its own choice when there are conflicting signals and may designate a different URL as canonical. This is reported in Search Console as “Google-selected canonical.”

Tip: Every page should include its own self-referencing canonical (that is, the page indicates its own URL as canonical). This minimizes the risk of misinterpretation and provides insurance against duplicate content issues.