Many web servers can compress data prior to sending it, using a variety of different compression methods. When a client makes a request of a server, it includes the Accept-Encoding header which informs the server which encoding methods the client supports. WebCopy supports the following compression methods
Disabling compression will cause the Identity value to be sent for the Accept-Encoding header, informing the web server not to compress content before serving it.
Encoding options generally only apply to static content, such as HTML, CSS and JavaScript. Other files such as Pdf or Zip are already compressed and normally won't be recompressed by a server.
It is recommended to always ensure that at least Deflate and GZip options are enabled as this helps makes downloads of HTML and static content smaller and faster.
Some servers may not support all available compression options. If you receive 406 (Not Accepted) errors when trying to copy a website, specifying an unsupported encoding could be the cause.