Clearly Digg Has Thought This Through Thoroughly

From Digg VP of engineering John Quinn’s description of the DiggBar:

We always represent the source URL as the preferred version of the URL to search engines and use the meta noindex tag to keep DiggBar pages out of search indexes. For those of you interested in the technical details, we also include link rel="canonical" information to indicate that the original URL is the real (canonical) version.

From Google’s FAQ regarding rel="canonical":

Can this link tag be used to suggest a canonical URL on a completely different domain?

No. To migrate to a completely different domain, permanent (301) redirects are more appropriate. Google currently will take canonicalization suggestions into account across subdomains (or within a domain), but not across domains.

(Thanks to DF reader Jakob Egger.)

Sunday, 12 April 2009