A Canonical URL Tag is an HTML element used in SEO to indicate the preferred version of a web page when multiple pages have similar or duplicate content. It helps search engines understand which URL to index and rank, preventing issues caused by duplicate content.
Synonyms: canonical link tag, canonical URL element, canonicalization tag, rel canonical

Duplicate content can confuse search engines, leading to lower rankings or split link equity. The canonical URL tag tells search engines which page is the original or most important version, consolidating ranking signals and improving SEO performance.
You add a canonical tag in the section of your HTML code. It looks like this: <link rel="canonical" href="https://www.example.com/preferred-page" />. This tag points to the URL you want search engines to treat as the main version.
If you have a product page accessible via multiple URLs due to tracking parameters or sorting options, use the canonical tag to point all variations to the main product page URL. This avoids duplicate content penalties and keeps your SEO efforts focused.