The SEO world is in a major tizzy this week with news that the major search engines have banded together to support a new “canonical url tag”, which will help combat many sites’ issues with such things as duplicate content and multiple versions of the same URL. For some background, I suggest you read our past post: “1 URL per page. Perhaps the most important information you’ll get today“, and the accompanying linked article from Jane and Robot.
Done? Good. Now you can see why this latest “canonical url tag” is such a major occurence in the SEO world. More testing needs to be done with this new tag to see exactly how the search engines will treat it, but most of the information you would need is provided in this post. Some choice excerpts:
Is rel=”canonical” a hint or a directive?
It’s a hint that we honor strongly. We’ll take your preference into account, in conjunction with other signals, when calculating the most relevant page to display in search results.Can I use a relative path to specify the canonical, such as <link rel=”canonical” href=”product.php?item=swedish-fish” />?
Yes, relative paths are recognized as expected with the <link> tag. Also, if you include a <base> link in your document, relative paths will resolve according to the base URL.Is it okay if the canonical is not an exact duplicate of the content?
We allow slight differences, e.g., in the sort order of a table of products. We also recognize that we may crawl the canonical and the duplicate pages at different points in time, so we may occasionally see different versions of your content. All of that is okay with us.What if the rel=”canonical” returns a 404?
We’ll continue to index your content and use a heuristic to find a canonical, but we recommend that you specify existent URLs as canonicals.What if the rel=”canonical” hasn’t yet been indexed?
Like all public content on the web, we strive to discover and crawl a designated canonical URL quickly. As soon as we index it, we’ll immediately reconsider the rel=”canonical” hint.Can rel=”canonical” be a redirect?
Yes, you can specify a URL that redirects as a canonical URL. Google will then process the redirect as usual and try to index it.What if I have contradictory rel=”canonical” designations?
Our algorithm is lenient: We can follow canonical chains, but we strongly recommend that you update links to point to a single canonical page to ensure optimal canonicalization results.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. So site owners can suggest www.example.com vs. example.com vs. help.example.com, but not example.com vs. example-widgets.com.Sounds great—can I see a live example?
Yes, wikia.com helped us as a trusted tester. For example, you’ll notice that the source code on the URL http://starwars.wikia.com/wiki/Nelvana_Limited specifies its rel=”canonical” as: http://starwars.wikia.com/wiki/Nelvana.The two URLs are nearly identical to each other, except that Nelvana_Limited, the first URL, contains a brief message near its heading. It’s a good example of using this feature. With rel=”canonical”, properties of the two URLs are consolidated in our index and search results display wikia.com’s intended version.
All in all,this development is something EVERY site owner should be paying particularly close attention to.
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If you’d like to chat to the Elite SEO, the Brisbane SEO agency, regarding anything that’s been mentioned in today’s post, please don’t hesitate to get in touch.
