Google: rel=”canonical” Now Supported In HTTP Headers

Jun 17, 2011 at 8:59am ET by Barry Schwartz

Google announced they are now supporting the rel=”canonical” attribute within HTTP headers.

This enables webmasters to set up a canonical for linking to or from PDF files or other non-HTML based files.

One of the examples given by Google is that a “webmaster can signal to Google that the canonical URL for the PDF download is the HTML document by using a rel=”canonical” HTTP header when the PDF file is requested.”

This also comes in handy when you use a CDN (content delivery network) and the content is being served from many different URLs. You can now use the rel=”canonical” within the HTTP header to set up those redirects for that type of content.

About The Author: Barry Schwartz is Search Engine Land's News Editor and owns RustyBrick, a NY based web consulting firm. He also runs Search Engine Roundtable, a popular search blog on very advanced SEM topics. Barry's personal blog is named Cartoon Barry and he can be followed on Twitter here. For more background information on Barry, see his full bio over here. See more articles by Barry Schwartz

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4 Comments on Google: rel=”canonical” Now Supported In HTTP Headers

Sebastian, June 17th, 2011 at 9:22 am ET:

History:

September 2009: tweeted https://twitter.com/ianmacfarlane/status/4499303411 by Ian Macfarlane

December 2009: outlined http://sebastians-pamphlets.com/x-canonical-uri-http-header/

April 2010: considered http://maileohye.com/rel-canonical-non-html-files/

June 2011: launched http://googlewebmastercentral.blogspot.com/2011/06/supporting-relcanonical-http-headers.html

P.M., June 17th, 2011 at 9:44 am ET:

But what are the benefits of using the rel=”canonical” HTTP header? Is that solution really useful you think?

Glenn Ferrell, June 17th, 2011 at 10:49 am ET:

I’d be interested in hearing any discussion of any possible linkages between this move (relative to CDNs) and Google’s Panda offensive against content farms. I haven’t had enough coffee yet to get my head around this :P

Nancy E. Wigal, June 17th, 2011 at 11:40 am ET:

Barry, excellent point about content going different places. I’m always amazed at the number of people who don’t know the power of canonicalization. Great article – thanks for posting!

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