Well... I mean, it's Factorio. Everything including the base game is a mod. :)
Silliness aside, it's a built-in part of "Multiplayer," which is included with the base game. But my late-night brain refused to use the word "Multiplayer" in an instance where only a single player (me) has ever been involved.
Like Quake was back in the day, online/multiplayer play of Factorio requires servers, and those servers are all run by regular-ish people. Some servers are public and are easy to find (and as with Quake, sometimes this is unintentional), and some [like my own] are private, unlisted, and don't even exist on the public Internet.
Silliness aside, it's a built-in part of "Multiplayer," which is included with the base game. But my late-night brain refused to use the word "Multiplayer" in an instance where only a single player (me) has ever been involved.
Like Quake was back in the day, online/multiplayer play of Factorio requires servers, and those servers are all run by regular-ish people. Some servers are public and are easy to find (and as with Quake, sometimes this is unintentional), and some [like my own] are private, unlisted, and don't even exist on the public Internet.