Images SEO - subdomain or different domain?

[stavros]

For a site with a very large number of images that are served by a CDN, is it better for that CDN to be a subdomain of the main domain (cdn.example.com) or a completely different domain (exampleimages.com)?

Does it make any difference? I'm thinking mainly about ranking the images in Google Image Search, but also about any effect on ranking the pages in Web search.

(I'm not considering the subfolder approach (example.com/images/) for infrastructure reasons, and also because I understand there is an SEO advantage to the page due to page speed if the pages are served from a different connection from the browser.)

[tedster]

You're right that a sub-folder approach will not improve a browser's ability to run parallel threads, so it won't increase page speed.

That said, page speed is not a major ranking factor - at least not so far. So I can't see how a fine point, such as subdomain versus stand-alone domain, is going to make any difference in Image Search ranking. The subdomain approach does seem like a better idea to me from a branding point of view.

[deadsea]

Don't know if a separate domain works for getting images ranked in image search, but I have had success with a subdomain CDN.

[TheMadScientist]

I don't usually have anything to do with image rankings, but I can tell you:

1.) If you host on http://example.com/ you will probably need to use a different site to host to get the full speed benefits, because if you use http://cdn.example.com/ cookies from http://example.com/ will be sent and if you're going to move them for search / speed purposes you might as well do it right.

2.) Where ever you decide to host them, make sure you 'set the home directory' of the sud-domain or new site to the current domain and block / redirect access to anything except the images back to the main domain, or 'point' the new site / sub-domain directly to the images location on the current site and adjust your links, because if you move the images physically to the new domain or sub-domain you create a management PAIN IN THE A** (Been there, done that.).

In short: I recommend keeping the images right where they are in the site structure, but changing where they are requested from, rather than physically moving them if at all possible.

[stavros]

Thanks for the responses.

page speed is not a major ranking factor

Do you mean you think it's still a very minor factor?
It's nearly a year since it was introduced as a factor by Google which would affect only "1% of queries":
[googlewebmastercentral.blogspot.com...]
We certainly seem to get far more pages crawled and indexed since improving load time, so it feels to me like it's becoming increasingly important.

(Perhaps a discussion for a different thread, but definitely relevant here.)

[tedster]

Site performance can definitely help crawling and indexing - but ranking is a different story. There can certainly be a secondary effect when a site is better crawled and indexed, and because also because a faster site improves user satisfaction. But as a direct ranking factor, performance/speed still looks weak to me.