So virtually everyone has weighed in on the new instructions from Google, Yahoo and Microsoft. Apparently there should be joy in the cesspool today - the search gods have shown us the way to clean up part of the confusion with canonical pages in our industry.
Okay, I know that sounds a little cynical, but like the no follow tag from a few years ago - it falls upon the web site owners to clean up the search engines' databases. Many knowledgeable site owners have already done a lot of this work in one form or another - though users of most dynamic sites have had a problem with multiple urls pointing to the same content (the same page really arrived at through different urls).
Interestingly even the engines themselves seem to have different views on what this new tag means. If you read the three announcements you could almost be excused for thinking they were describing different things.
Yahoo wins the most confusing explanation, while Google adds art that really adds little unless you need visuals of the same page with different text pointing to it - but does do a decent job of simplifying the instructions, but Microsoft does it briefly and clearly then tells us they will be implementing it "sometime in the near future."
It sort of reflects the positions each has in the search space. Google with their monster share see us as children, Yahoo as number two tries harder, while Microsoft gives it the same attention it gives to its flagging search percentage - short but sweet.
To be fair Yahoo may offer the most thorough explanation (you just may have to read it a couple of times) and points out a caution "if URL A marks B as canonical, and B marks C as canonical, we'll treat C as canonical for both A and B, though we will break infinite chains and other issues."
Interestingly, if they had published a shared announcement they would have given an example of what many people think of when they hear the term duplicate content - the same copy/text/content on different websites. This is not about that issue.
It can, however act as a 301 redirect within a domain - good for removing those www.domain, domain.com, domain.com/index.html etc problems, but not from one domain to another domain
However, this tag "defines a relationship between a document and an external resource" as Microsoft states. The fact that they are calling it a link tag scares me a little, just like the no follow one did when it came out.
People are going to get this wrong, just like they did the no follow and it will dramatically impact sites. But, I suppose we can feel okay because none of the engines have committed to using it 100%.
Google has already stated there will be penalties for anyone using it to game their results.
Thanks should go to Vanessa Fox for a solid interpretation "this tag will only work with very similar or identical content, so you can't use it to send all of the link value from the less important pages of your site to the more important ones.
If tags conflict (such as pages point to each other as canonical, the URL specified as canonical redirects to a non-canonical version, or the page specified as canonical doesn't exist), search engines will sort things out just as they do now, and will determine which URL they think is the best canonical version."
Kudos to Joost de Valk for his same day roll out of plugins for WordPress, Drupal and Magento E-Commerce. He did have a few days advanced notice but the effort will be much appreciated by many.
There have been a bunch of posts about this, so mine is just another, and comments throughout Twitter. I am not as enthusiastic as Rand Fishkin who sees it as "the most important advancement in SEO since sitemaps." Guess I would be closer to Mikkel deMib's view posted on Twitter. "The new canonical tag is like adding a cheap layer of pain to a crappy car. Sorry guys, it doesn't make the car much better!"
It will be interesting to get more opinions on all this next week at SES London.