MaxCDN Blog

Better Image SEO with Canonical Headers

April 25, 2014

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:

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.

To fix the issues they’ve listed above, we’ve added a “Canonical Header” option to the Control Panel (under Pull Zone SEO settings):


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/1.1 200 OK
Date: Wed, 16 Apr 2014 23:15:22 GMT
Content-Type: image/png
Content-Length: 5565
X-Cache: HIT
Link: <>; rel="canonical"

For MaxCDN Enterprise customers, we have added a new EdgeRules category called “SEO”.  The first rule to chose from is “Add Canonical Header” which gives you more more control by allowing you to choose which file types you would like to apply the Canonical header to:


And there you have it — the link header being sent back, pointing to the canonical source. Go forth and enjoy this 1-click SEO boost.

  • dinkuminteractive

    Hi David,

    Really happy to see you blogging on this topic, since it has been a consistent challenge for us after moving a bunch of clients to MaxCDN.

    The default settings have not worked out well for our clients -> we’ve only found true success by asking google to index the CDN instead of the origin. My hunch is that unless your rules engine can force Googlebot to always get the origin when crawling the site, they see all kinds of references to the CDN assets out there in the world (e.g. social sharing, on the page) and even though canonicalization is in use, it sniffs out the duplicate content.

    My question: do you have any uses cases showing Google Webmaster Tools index stats before/after your recommended change? See attached for my opposite experience, which goes from the “one click SEO boost” approach to the approach outlined above.

    I’ve repeated this scenario now with 6 sites on MaxCDN, but would love to find a strategy in which i could encourage indexing of the origin instead of the CDN.

  • dinkuminteractive


    Sorry another reply as I was circling back to your post this afternoon. Are you using your own CDN on this blog for image serving? I see images are served from here:

    I guess I would be interested how well your blog and the MaxCDN site index images with your recommended settings, which I assume you are using. Care to share Google Webmasters data with us?

  • David Henzel

    Thank you for your feedback! We have built this based on best practices and feedback from SEO experts. We have not done a case study on it, but it would be great to work you on this. We can enable Edge Rules for you so we can fine tune your account together. Please shoot me an email in case you are interested. (david (at)

  • Aleksei Humeniuk

    Hi David,

    Thank you for interesting post.

    Google currently supports canonical link header elements for Web Search only. So, how can your method help websites, if Google don’t use canonical for image search?