What happens when two players reach zero life at the same time due to state-based actions?

State-based actions are checked and applied simultaneously whenever a player would receive priority (CR 704.3). If multiple state-based actions are applicable at the same moment, they all happen at once — none is checked before another.

One of those state-based actions is CR 704.5a: 'If a player has 0 or less life, that player loses the game.' When this condition is true for two or more players at the same time, all of them lose simultaneously.

When all remaining players lose simultaneously, the game is a draw per CR 104.4b: 'If all the players remaining in a game lose simultaneously, the game is a draw.' This is not a tie in the colloquial sense — it is a specific game outcome distinct from a win or a loss.

Concrete example: Alice is at 2 life and Bob is at 1 life. Alice controls a creature with 'Whenever this creature attacks, each player loses 2 life.' The creature attacks, the triggered ability resolves, and both players drop to 0 or below simultaneously. State-based actions are checked: both have 0 or less life (CR 704.5a), both lose at the same time, and the game ends in a draw.

Note: This also applies in multiplayer — if the last two remaining players both reach 0 life at the same time, the whole game is a draw (CR 104.4b). If there were still other players in the game, those other players would remain and the game would continue.