NOTE: XMPP compression has unresolved security concerns, and this module has been removed from Prosody and renamed.

While the bandwidth usage of XMPP isn’t that much, compressing the data sent to/from your server can give significant benefits to those on slow connections, such as dial-up or mobile networks. Prosody supports compression for client-to-server (if your client supports it) and server-to-server streams using the mod_compression plugin.


mod_compression implements XEP-0138, and supports the zlib compression algorithm.


The XMPP protocol specifies that all clients and servers supporting compression must support the “zlib” compression method, and this is what Prosody uses. However you will need to install zlib support for Lua on your system. There are different ways of doing this depending on your system. If in doubt whether it is installed correctly, the command lua -lzlib in a console should open a Lua prompt with no errors.

apt-get install lua-zlib
luarocks install lua-zlib


modules_enabled = {
    -- Other modules
    "compression_unsafe"; -- Enable mod_compression_unsafe


The compression level can be set using the compression_level option which can be a number from 1 to 9. Higher compression levels will use more resources but less bandwidth.


modules_enabled = {
    -- Other modules
    "compression_unsafe"; -- Enable mod_compression_unsafe
compression_level = 5


With the plugin installer in Prosody 0.12 you can use:

sudo prosodyctl install --server= mod_compression_unsafe

For earlier versions see the documentation for installing 3rd party modules