What happens if both players draw from an empty library at the same time?

When a player is required to draw a card from an empty library, they don't lose immediately upon the draw attempt — instead, they lose the next time a player would receive priority (CR 704.5b). This is handled through the state-based actions system, which checks all applicable conditions at the same time.

If both players are simultaneously required to draw from an empty library — for example, both are forced to draw during the same event — then when state-based actions are checked, both players are found to have drawn from an empty library. State-based actions affecting multiple players are all performed simultaneously (CR 704.3). This means both players lose at exactly the same time.

When all players lose simultaneously, the game is a draw (CR 104.4b). No player is considered the winner. In a tournament setting, this typically means both players receive a draw result for the match.

Concrete example: It's your opponent's turn and they cast Windfall while both players have empty libraries. Both players must draw cards and cannot. When state-based actions are checked, both players have attempted to draw from an empty library, so both lose simultaneously — the game is a draw.

Note: If only one player has an empty library, only that player loses (CR 704.5b). The simultaneous draw outcome specifically requires both players to trigger the losing condition at the same check.