Better Image SEO with Canonical Headers
Customers often ask us if having the same image on different servers could impact SEO. We now have an official answer, as Google blogged about image indexing:
To fix the issues they’ve listed above, we’ve added a “Canonical Header” option to the Control Panel (under Pull Zone SEO settings):
Q: “Is it a problem if my images can be found on multiple domains or subdomains I own — for example, CDNs or related sites?”
Generally, the best practice is to have only one copy of any type of content. If you’re duplicating your images across multiple hostnames, our algorithms may pick one copy as the canonical copy of the image, which may not be your preferred version. This can also lead to slower crawling and indexing of your images.
This option adds a HTTP header to cached objects on the CDN, telling search engines the location of the original file on your origin server. With this information, services like Google Image Search can link to the original source in search results, and avoid crawling the same content multiple times, saving you bandwidth.After enabling Canonical Headers, use curl or your browser dev tools to inspect the headers coming back from the CDN:
curl -I http://w3.example.netdna-cdn.com/images/matt-cutts.jpg
HTTP/1.1 200 OK
Date: Wed, 16 Apr 2014 23:15:22 GMT
Link: <http://www.example.com/images/matt-cutts.jpg>; rel="canonical"