This is a selected list of multiplayer online games which are free to play in some form without ever requiring a subscription or other payment.
Some common types are first-person shooters or multiplayer online battle arena, but could be of any genre.
These MOGs run on a non-profit basis, requiring no payment from the players.
These MOGs run on a for-profit basis, and do not require money from the player for an in-game advantage over other players.