What domain should we use for anonymous external direct image linking?

Question

I often need to get a direct link URL to an image in one of my public galleries in a circumstance where I do not want the URL to lead back to my web site - so I want the image URL to be anonymous and I've never really understood what the best domain to use for these anonymous URLs is. Over the years, I've found that I can take an image URL like this:

http://jfriend.smugmug.com/Kenya/Highlights/Landscapes/JF23827/344291068_HdnTo-M.jpg

and I can change it to:

http://photos.smugmug.com/photos/344291068_HdnTo-M.jpg

and it becomes a somewhat anonymous URL that doesn't show my site or the category, sub-category or gallery of the image.

But, there are many different domains that could be used. Are any of those domains better than the others? These are the candidates I've found that work:

http://cdn.smugmug.com/photos/344291068_HdnTo-M.jpg
http://api.smugmug.com/photos/344291068_HdnTo-M.jpg
http://photos.smugmug.com/photos/344291068_HdnTo-M.jpg

Note that http://www.smugmug.com/photos/344291068_HdnTo-M.jpg does not work for this purpose because it redirects to my domain and doesn't stay anonymous.

This question is related to this one, but that other question is specifically about URLs returned from API requests, not manually created URLs for anonymous use like this.

Which domain is the preferred domain to use for best performance and best reliability in the long term (e.g. no Smugmug changes that might break the URL)?

Answer 1

As you've found, technically any of the three will work. But 'photos.smugmug.com' is the domain that's really designed for this. It goes through the properly scaled layers of our architecture, from CDN to caches to photo-optimized serving clusters, and does the 'right thing'.

The others will also work, and you probably won't even notice the difference, so there's technically no harm using any of the above.

We try hard to do proper redirects (or, in some cases, error messages) when a 'wrong' URL is used, so if those weren't also valid URLs, we'd already be sending you back to one that was. :)