Forum
Notifications
Clear all
Topic starter
Carpe diem on any duplicate content worries: we now support a format that allows you to publicly specify your preferred version of a URL. If your site has identical or vastly similar content that's accessible through multiple URLs, this format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version.
Let's take our old example of a site selling Swedish fish. Imagine that your preferred version of the URL and its content looks like this:
http://www.example.com/product.php?item=swedish-fish 
However, users (and Googlebot) can access Swedish fish through multiple (not as simple) URLs. Even if the key information on these URLs is the same as your preferred version, they may show slight content variations due to things like sort parameters or category navigation:
http://www.example.com/product.php?item=swedish-fish&category=gummy-candy 
Or they have completely identical content, but with different URLs due to things such as a tracking parameters or a session ID:
http://www.example.com/product.php?item=swedish-fish&trackingid=1234&sessionid=5678
Now, you can simply add this <link> tag to specify your preferred version:
<link rel="canonical" href="" http://www.example.com/product.php?item=swedish-fish" ;" />
inside the <head> section of the duplicate content URLs:
http://www.example.com/product.php?item=swedish-fish&category=gummy-candy
http://www.example.com/product.php?item=swedish-fish&trackingid=1234&sessionid=5678
and Google will understand that the duplicates all refer to the canonical URL: http://www.example.com/product.php?item=swedish-fish. Additional URL properties, like PageRank and related signals, are transferred as well.
This standard can be adopted by any search engine when crawling and indexing your site.
Is rel="canonical" a hint or a directive?
It's a hint that we honor strongly.
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?
Slight differences are allowed, e.g., in the sort order of a table of products. Search engines also recognize that they may crawl the canonical and the duplicate pages at different points in time, so they may occasionally see different versions of your content.
What if the rel="canonical" returns a 404?
Search engines will continue to index your content and use a heuristic to find a canonical, but it is recommended that you specify existent URLs as canonicals.
What if the rel="canonical" hasn't yet been indexed?
Like all public content on the web, search engines strive to discover and crawl a designated canonical URL quickly. As soon as it got indexed, search engines will 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?
Canonical chains can be followed, but it is strongly recommended 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?
The answer is yes!
Posted : 18/04/2011 11:01 am