Google has today announced that they now officially support rel=’canonical’ HTTP headers. Below is a quote from the Google Webmaster Central Blog: “Based on your feedback, we’re happy to announce that Google web search now supports link rel="canonical" relationships specified in HTTP headers as per the syntax described in section 5 of IETF RFC 5988. Webmasters can use rel="canonical" HTTP headers to signal the canonical URL for both HTML documents and other types of content such as PDF files.”
Take a look at their blog – examples are given of its implementation and there will no doubt be a range of feedback as usual in the comment there. The specifics of the syntax to be used can be found here: It doesn’t look like Google is removing the existing <link> canonical support, but rather providing more options for webmasters to implement it where it is a struggle to put in place at a page level. This is a good, confidence-inspiring move by Google. It shows that they are confident that rel canonical is working as a concept, and that they can confidently recognise and disregard incorrect implementations and potential malicious uses of it (as spoken about recently by Matt Cutts). Our experience is certainly that it is a very powerful tool when used properly. There isn’t any mention of cross domain support yet, but given the way the <link> version of the canonical tag developed is, it will most likely follow once Google is happy with this initial rollout. Offering more ways for webmasters to ‘tidy up’ duplicate content is very much in line with the various Panda updates we’ve seen over the past few months, and may potentially be used as a way to help fix Pandalized sites / pages. On a separate note it was announced at SMX Advanced earlier this month that Panda update 2.2. is on its way. More on that once it is rolled out!