Amazon CloudFront can now compress your objects at the edge. You can now configure CloudFront to automatically apply GZIP compression when browsers and other clients request a compressed thing with text and other compressible file formats. This means that whether you are already using Amazon S3,CloudFront can transparently compress this type of content. For origins external S3, doing compression at the edge means you don’t need to use resources at your origin to do compression. The resulting smaller size of compressed objects makes downloads faster and reduces your CloudFront data transfer charges.
Source: amazon.com