The Content Compression rule

This rule checks values in the Content-Type header an origin response and enables compression for the specified content.


You should review the list of Content Types in the match and update the list as needed. For example, you may prefer not to compress JavaScript content, so you would remove the application/x-javascript content type from the listing. If you click in the blank area of the listing, you’ll see that text/xml and text/plain are already suggested additions to the match values. You can click the blank area of the listing and type any Content-Type string to add it to the list. (It appears in the drop down, accompanied by "(new item)." Click the entry to add it.) Use the wildcard (*) at the end of your string to ensure that additional characters in the Content-Type definition don’t prevent the match from succeeding.

The Last Mile Acceleration (Gzip Compression) behavior

The Compress Response option is set to Always by default. The specified Content Types are compressed when the requesting end-user agent (browser or device type) supports Gzip unzipping. This can improve transfer times to clients with slow connections. Consider the following if you want to enable Last Mile Acceleration (LMA):

  • LMA is only useful for certain Content Types. This includes HTML, JavaScript, or UTF-8 character encoded, and then when the content is larger than roughly 10 KB.
  • LMA should be avoided with other Content Types (outside of what's listed above). For example, don't use it to compress images that are already compressed, or to compress small files that require more time to compress, send, and unzip, than would actually be saved in transmission time.
  • You can also choose to use what's set in your origin response headers for compression. If your origin headers already explicitly describe how compression shoiuld be handled for your content, set this to Same as origin response.