Can we detect if a site is on CDN?

A method that is achievable from the command line is using the 'host' command, with the -a flag set to see the DNS record e.g.

host -a www.visitbritain.com

Returns:

www.visitbritain.com.   0   IN  CNAME   d18sjq5nyxcof4.cloudfront.net.

Here you can see that the CNAME entry tells us that the site is using cloudfront as the CDN.

I built this little tool to identify the CDN used by a site or a domain, feel free to try it.

The URL: http://www.whatsmycdn.com/

Just take a look at the urls of the images (and other media) of the site. Reverse lookup IP's of the hostnames you see there and you will see who own them.