Despite high demand for multiplayer, Just Cause 4 will be a single-player game, though the door remains open for multiplayer to be added in the future. After being leaked in an ad on Steam, Just Cause 4 was officially unveiled by Square Enix during the Xbox showcase at E3.
The open-world sandbox series of action games, Just Cause, features so many opportunities for chaos and destruction that many have campaigned for the games to eventually provide multiplayer support. Since the developers never included it, fans made a multiplayer mod for Just Cause 2 that became incredibly popular. Some were disappointed when Just Cause 3 didn't feature multiplayer either, and as a result another fan-made mod was created in 2017. Both multiplayer mods have been met with extremely positive reviews.
In an interview with Polygon, Avalanche Studios game director Francesco Antolini talked about Just Cause 4 and the possibility of adding multiplayer support:
Just Cause 4 is going to be a single-player game, because we wanted to focus on a great single-player experience. I don’t exclude multiplayer in the future, but we need to see how things go.
One of the main arguments for multiplayer in a Just Cause game is how the series feels perfect for playing with others online. It's one of the reasons why the Just Cause 2 fan-made mod was so successful. The mod provided a major boost in sales and extended the life of the game in a big way. It's worth noting that the mod was even supported by the developers. Nevertheless, this didn't lead Avalanche Studios to add multiplayer to Just Cause 3. The fact that the third installment lacked multiplayer had a somewhat negative impact on reviews.
However, the developers have always defended the decision to leave multiplayer out of the games. As Antolini pointed out, Just Cause 4 is a single-player game, which means that the single-player experience takes priority. This sets Just Cause 4 apart from other games which once focused on offline, solo playthroughs that are now moving towards online play, such as Fallout 76. The announcement that Fallout 76 won't include any NPCs has earned a great deal of skepticism from its fanbase. Though some will be undoubtedly disappointed by the news that Just Cause 4 won't initially support multiplayer, there's still a chance for it to be added at some point down the road. Until then, players will have to be content with shooting NPCs instead of each other.
Just Cause 4 launches on December 4, 2018 for the Playstation 4, Xbox One, and the PC via Steam.