What is a canonical tag?
A canonical tag is a line of HTML, written as rel="canonical", that tells search engines which URL is the preferred version of a page when similar or identical content exists at more than one address.
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Why canonical tags matter
The same content can often be reached through several URLs, such as ones with tracking parameters, sorting options, or both http and https versions. Without guidance, search engines have to guess which one to show.
A canonical tag points them to your preferred URL, which helps consolidate signals like links onto one page.
How to use canonical tags
Place the tag in the head of the page, pointing to the full URL you want indexed. A page can also point to itself, which is a common practice that makes the preference explicit.
Make sure the canonical URL works, isn't blocked, and isn't redirected elsewhere. Conflicting signals can lead search engines to ignore the tag.
Common questions
Is a canonical tag the same as a redirect?
No. A redirect sends visitors and search engines to a different URL. A canonical tag leaves the page accessible but suggests which version should be treated as the main one.
Do search engines always follow canonical tags?
Not always. The tag is a strong hint rather than a command, and search engines may choose a different URL if other signals disagree.
Should every page have a canonical tag?
It's a common practice to give every indexable page a self-referencing canonical tag. It's most important where duplicate or near-duplicate versions of a page exist.
Can I use a canonical tag across different domains?
Yes. A cross-domain canonical can identify a preferred version of duplicate or very similar content on another domain. For syndicated articles, Google recommends partners block indexing if the aim is to keep their copies out of Search, rather than relying on canonicals.
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