https://www.gamespot.com/articles/red-dead-redemption-2s-online-multiplayer-coming-a/1100-6461880/

Rockstar has taken the wraps off of its plans for Red Dead Redemption 2's online mode, named simply Red Dead Online. As was the case with Grand Theft Auto V's online component, GTA Online, Red Dead Online will not launch alongside the game itself; instead, it will debut sometime in November 2018--one month after Redemption 2 itself releases--and will start as a public beta. Access will be free to owners of RDR2, and the announcement doesn't specify any plans to make it available separately.

"Using the gameplay of the upcoming Red Dead Redemption 2 as a foundation, Red Dead Online will be ready to be explored alone or with friends, and will also feature constant updates and adjustments to grow and evolve this experience for all players," the announcement states.