G-CDN servers support gzip compression. If origin supports gzip too, two versions of a content (compressed and uncompressed) will be stored in a CDN. Read more on gzip compression.
If gzip compression is not configured on your origin server, you can use the Compress on CDN option. This function allows you to compress files on a CDN side. At the same time, CDN servers will always request the uncompressed version of a content from your origin.
By default, this option is turned off. To enable it, expand the Advanced Settings section, find the Content subsection, click the Add Option button and select Compress on CDN. Save settings.