You’ve heard about the canonical tag right? Still confused on when to use it?
Well, Google’s Greg Grouthaus recently posted a video about duplicate content and multiple site issues on the Google Webmaster Central Blog. And as part of it, he did a refresher on when and when not to use the canonical tag.
Do canonical tags work across different domains?
No, they only work on the same domain. So you wouldn’t be able to use them on any ‘sister’ or partner sites you might have.
For example, a page on pinkcarpets.com wouldn’t be able to use a canonical tag to tell the search engines to index a page from pinkcarpetsclearance.com instead.
Ah, but do they work across subdomains (hosts)?
Yes – so a canonical tag could be used on a page on clearance.pinkcarpets.com to tell the search engines to index a page on blog.pinkcarpets.com instead.
Should I use a canonical tag instead of a 301 redirect?
It depends on the pages in question – remember that a 301 will permanently redirect search engines and your users.
But, if you had 3 pages for a product for example, and they are all exactly the same except for the product colour, it would be best to use a canonical tag. That way only one page would get indexed but users could browse all the product pages on the site.
And don’t forget, there are other ways to stop search engines indexing duplicate content. For example, by blocking pages in your robots.txt and by using the ‘noindex’ meta-tag.
Do the pages have to be identical?
As mentioned above in the product pages example, they don’t have to be exactly the same. But they need to be similar.
So using canonical tags in your ‘print’ pages would be fine, as they’re likely to be similar to your main pages rather than totally identical.
The key thing to remember is that a canonical tag is a ‘hint’ rather than an ‘order’ to the search engines. If they decide that 2 pages are not similar, they can ignore a canonical tag altogether.
Can I use a tag to specify an http page rather than an https page as the canonical URL?
Yes.
This also goes for different versions of your home page. For example:
- http://www.pinkcarpets.com/index.htm
- http://pinkcarpets.com
- http://www.pinkcarpets.com
Here, you could use a canonical tag to specify http://www.pinkcarpets.com as the canonical URL (the URL you want to be indexed).
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