I agree on the security side if you use that attribute. However: > And the performance of your CDN is probably worse than the Google CDN What means probably?

I agree on the security side if you use that attribute. However: > And the performance of your CDN is probably worse than the Google CDN What means probably? Other CDNs (Akamai, CloudFront, Cloudflare, etc) are also fast. And by pushing one piece of your website on a different CDN you force your users browser to create an additional HTTPS connection which takes additional round-trips, instead of being able to leverage one connection for all assets. This alone might as well outweigh the performance differences between CDNs. Also the "shared cache" benefit might go away, if I read the other answers in this topic correctly.