Chess Clock: Two Players, Two Clocks, One Running

Why two linked clocks, not two timers

The point of a chess clock is that time is zero-sum. There is no shared pool and no neutral state: every second belongs to exactly one player. Thinking for a long time is not free — it is spent from your own budget, and your opponent can watch you spend it.

This is why the multi-timer cannot substitute. Independent clocks can both run at once, or both be stopped, and nothing enforces the alternation. Here the alternation is the tool: only the player whose clock is running can pass the turn, and passing it necessarily starts the other clock. There is no way to leave the game in a state where nobody is on the clock.

The consequence is behavioural rather than technical. A player who knows their thinking is visibly draining a finite number tends to think differently — usually faster, and with a clearer sense of which decisions deserve the time.

Choosing a base time

Both players start with the same base time, set anywhere from one to 180 minutes; fifteen is a sensible default and the one the page offers. The number should come from how long you actually want the whole session to last, and the arithmetic is easy to get wrong in one specific way.

Because both clocks together total twice the base time, a fifteen-minute setting is a game of up to thirty minutes, not fifteen. People routinely set what they think is an hour and find themselves two hours in. Halve your intended total, and set that.

The setup locks once the first turn has been taken, so the terms cannot shift mid-game. Reset if you need to change them.

Increment: paying players back for moving

An increment adds a fixed number of seconds — up to 120 — back to a player's clock each time they complete their turn. The default is zero, which is a pure countdown of the base time and nothing else.

The problem an increment solves is specific and worth understanding, because it decides whether you want one. Without it, a game that goes long enough always ends the same way: both players run low, and the finish becomes a race to move quickly rather than well. The player who was winning on merit can lose to the player who is faster with their hand. An increment guarantees a small amount of time for every move, so the endgame stays a contest of judgement instead of dexterity.

A practical rule: use no increment for short, deliberately frantic games where the scramble is the entertainment. Use two to five seconds when you want a fast game that still ends on its merits, and ten or more when moves genuinely need thought and you would rather nobody lose on time at all.

Passing the turn

Each side has its own button to pass the turn, and only the player whose clock is currently running can press theirs — the other is disabled. This is not a limitation but the rule of the instrument: you stop your own clock, which starts your opponent's.

The etiquette that comes with real chess clocks applies here too, and it exists to prevent a genuine unfairness. Complete the action, then press. In chess that means moving the piece with one hand and pressing with the same hand; in any other use it means finishing what you were doing before stopping the clock. Pressing first and then acting steals time from your opponent, because your action is happening on their clock.

The shared pause stops both clocks — for a genuine interruption, not for thinking. Pausing to consider a move is simply taking time without paying for it, which defeats the point of the exercise. Reset returns both clocks to the base time and clears the round count.

Running out, and recording who won

When a clock reaches zero the session ends immediately, a low tone sounds, and the other player is declared the winner. This is the traditional rule — running out of time loses the game regardless of the position — and it is enforced rather than merely announced: neither clock will restart afterwards.

When you save the session, the result can be set explicitly to either player or a draw, or left on automatic, which awards it to whoever has more time remaining. Automatic is right when time was the contest. It is wrong whenever the outcome was decided by something the clock cannot see — a checkmate, a resignation, a concession in a debate — and in those cases you should set the winner yourself, because a saved history of results that quietly disagrees with what actually happened is worse than no history at all.

The number of rounds played is counted for you and saved with the session, along with each player's remaining time and their names. Naming the players is worth the four seconds: a history of "Player A beat Player B" eleven times tells you nothing at all.

Uses that have nothing to do with chess

Any situation where two people share a limited amount of speaking or thinking time has the same shape, and benefits from the same instrument.

• Debates and structured arguments — each side gets an equal budget and spends it as they choose, which is far fairer than policing individual speeches.
• Two-player board games — Go, backgammon, draughts, and any game with a player prone to very long turns.
• Interviews and one-to-ones — as a check on the common failure where the person asking the questions uses most of the time.
• Children sharing something — a screen, an instrument, a game. The clock is neutral in a way a parent is not, which removes the argument entirely.

For sequences of timed blocks rather than two alternating players, the interval timer is the better fit; for several unlinked clocks, the multi-timer.