A chess timer is a clock with two countdowns — one for each player.
At the start, both players have a set amount of time, for example, 10 minutes each, or one player can be given more time to even out a game.
When Player 1 makes a move, they tap their side of the timer. Their countdown stops, and Player 2’s countdown starts.
This back-and-forth continues: only one clock runs at a time, depending on whose turn it is.
If a player’s time runs out before the game ends, they lose on time, no matter the board position.
This ensures games don’t last forever and adds strategy: you must manage both your moves and your remaining time.