Such modifications have been unofficially supported by Overkill with the addition of the mod_overrides system (see Tools below) which allows the game to load unpacked assets from a special folder in place of archived files. Only has an impact on the mod user's experience, even if said player is the host. The two most common types of clientside mod are texture and sound mods these modify the textures or sounds of various objects, characters or environment.

Clientside (/mod_override) mods are generally safe to use in online play - they often have little (if any) impact on the experience of other users, and will be unnoticeable to other players.