Canonical tag explained simply: avoid duplicate content
What the canonical tag does
The canonical tag is a line in the header of a page that points to the preferred address. It tells search engines: This content belongs under this URL. Signals from variants are then consolidated to the preferred address.
Typical cases
- Tracking parameters such as ?utm_source=newsletter.
- Sorting and filtering parameters in shops.
- Print versions or variants of a page.
- The same product page in multiple categories.
Canonical or redirect?
A redirect sends visitors elsewhere – it is appropriate when the old address is no longer needed, for example after a relaunch. The canonical tag makes both addresses accessible and is a hint, not an instruction.
Typical relaunch error
After the Go-Live, canonical tags still point to the test environment or the old domain. Google may follow this hint and index the wrong address. Therefore, check the canonical tags of important pages on the first day.
Frequently asked questions
It is good practice for each page to link to itself. This automatically covers parameterized variants.
Not always. It is a strong indicator; if other signals such as internal links or the sitemap contradict it, Google may decide differently.
No, if the page has a canonical tag pointing to the address without parameters. Then Google consolidates the signals.
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