What Is Rel=canonical?
Without correct canonical tags, you risk Google splitting your ranking power across multiple URL variants — a common problem with e-commerce filters, pagination, and tracking parameters. Especially after website migrations, incorrect canonicals are often overlooked: when the new page points to the old URL as its canonical, Google does not index your new version. Check your canonicals regularly via Google Search Console.
rel=“canonical” (or canonical tag) is an HTML element that indicates the preferred version of a page in case of duplicate content. This element is placed in the <head> section of an HTML page and helps Google understand which version of a page is the “main version” when multiple URLs contain the same or very similar content. Example: if a product page is accessible at /product?id=123 and also at /product-name, the canonical tag shows which URL Google should treat as the primary version. This prevents Google from splitting ranking power across multiple URLs.
Technically, the canonical tag is embedded in the <head> of a page: <link rel="canonical" href="https://www.example.com/preferred-url" />. A canonical tag can refer to itself (e.g., to /product/) and thereby indicates that this is the primary version. Alternatively, a page can point to a different URL — this is especially useful for session IDs, tracking parameters, or filter variants. Google respects canonical tags strongly but not absolutely — if two versions are very different or the canonical is obviously incorrect, Google ignores it. It is especially important not to create a canonical loop (A points to B, B points to A), as this confuses Google.
In practice, every website should have a well-thought-out canonical tag system. E-commerce websites often need canonicals for filter variants, pagination, and URL parameters. News websites can manage syndications with canonicals pointing to the original source. WordPress often uses automatic canonicals. A common mistake is that canonical tags are forgotten during website migration — then the new website points to the old URL as its canonical and Google does not index the new page. This should be regularly checked via Google Search Console.
Über den Autor
Christian SynoradzkiSEO-Freelancer
Mehr als 20 Jahre Erfahrung im digitalen Marketing. Fairer Stundensatz, keine Vertragsbindung, direkter Ansprechpartner.