If you are using CDN you may have a separate host for it (eg cdn.yoursite.com), and the original site URL should be replaced with it.

On Swift Performance Settings > CDN tab, you can set up your CDN hostname(s), to use CDN URL for media-, CSS and javascript files automatically. You can use separate hosts for each file type, or specify only one host for all static content.

You can specify a different hostname for SSL version of the page, however it is a legacy feature, for a properly configured website you won’t need this.

If you are using Cloudflare as CDN you don’t need enable CDN in Swift settings. See more info: Cloudflare Integration

By default Swift Performance will use CDN for the following file types:

css,js,jpg,jpeg,png,gif,swf,flv,mpeg,mpg,mpe,3gp,mov,avi,wav,flac,mp2,mp3,m4a,mp4,m4p,aac,webp

 

If you would like to use CDN for custom file types, you can specify it one-by-one. Use the extension (eg pdf) without the leading dot.

You can also exclude specific file types on the same way as you can include custom ones: specify file extensions one by one, (eg: pdf)