With the release of the Xbox Store page for Crackdown 3 it is revealed that the game will only support two player coop. This is in comparison to the originally promised four player coop that was supposed to be present. That note of support for having four players in online coop is even still mentioned on the game's special splash page. The two player coop capability is noted on the actual store page in terms of having a banner note as well as having it specifically mentioned within the description of the game.
"Play the campaign solo or with a friend in co-op mode". The game is a Xbox Play Anywhere title available for Xbox One or Windows 10 PC. With that, it will support cross-play coop if you'd like to play with someone on either platform. The online functionality will require Xbox Live Gold to access. For context, this is the latest entry in the franchise that has received many delays. It is all about explosions and enhancing your Agent while battling various wild factions. You can read the details on the Xbox One X enhancement below or view the hub for franchise to see additional coverage on the series.
Xbox Store Page
Read our Crackdown 3 Xbox One X Enhanced Details
View our Crackdown Hub