Apache Reference: mod_mime, AddEncoding

AddEncoding

Associate MIME Content Encoding with File Extension
Syntax: AddEncoding mime-enc file-ext [file-ext ...]
Example: AddEncoding x-gzip .gz
Since: Apache 1.0

This directive maps a given file name extension to the specified MIME encoding type one or more times. The mime-enc argument is the MIME encoding used for documents with the file extension file-ext. This mapping is added to any already in force, and it overrides any existing mappings for the same extension.