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Chess Clock

Run two mutually exclusive chess clocks with a Fischer increment, reversible clock presses, and a private daily move-press history instead of trying to reconstruct a game from a plain tally.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose the initial seconds and Fischer increment before starting; the displayed initial time includes the increment required before move one.
  2. 2.Start White or Black, then press the clock after each move to credit that player and switch the active side; Pause materializes elapsed time.
  3. 3.Use Undo last press for an accidental tap, review local daily press history, and export PNG or CSV only when you need a private copy.

About Chess Clock

Chess Clock is a local practice timer for the part of a chess game that a generic counter cannot represent: only one player may be thinking at a time. Set an initial time and an optional Fischer increment, start White or Black, then press the clock after a move. The active player's time stops, the other player's time begins, and the player who pressed receives the configured increment. The large two-column display keeps both remaining times visible without asking you to calculate a bonus in your head. It works well for a casual over-the-board game, a study session, a blitz drill, a club practice board, or a lesson where the players need a simple shared rhythm rather than a full online chess service.

The time-control behavior is deliberately explicit. FIDE's current electronic-clock specifications describe Fischer increment controls and require the increment before move one; the Laws of Chess define a clock press as stopping the player who moved and starting the opponent. This tool follows that simple add-after model: the initial display includes the increment, and each completed press switches the active side after crediting the side that pressed. It does not treat Fischer increment as delay. A delay has different behavior and is not included here. The timing rules are implemented as a small tested state machine with separate white time, black time, an active side, an optional flag, and an elapsed-time anchor. That is safer than letting two independent countdowns run or trying to infer who should receive a bonus from a single number.

The clock is private by design. Each completed press also creates a count in the device-local calendar day history, so you can see how many moves were timed on a particular day. Undo last press restores the full prior clock snapshot and removes the associated daily press count. This matters when a player taps the clock accidentally: a generic minus button cannot know which side was active or how much increment belonged to that press. Pause materializes the currently running time and leaves both clocks stopped. A flagged clock reaches 00:00 and prevents further move presses until you set a new time control. The practice interface does not try to judge a chess position, determine a result, manage move numbers, or replace an arbiter.

Export stays in your browser. Export PNG creates a natural 1080 by 1350 image showing the private daily total and recent days, with no URL and no player identity. Export CSV creates one Date and Completed clock presses row per saved day for a spreadsheet or personal archive. Both use native browser Blob and canvas APIs. There is no account, upload, cloud synchronization, remote chess server, or scoring API. The current time control and daily press history are stored only under this tool's local browser key. Another device begins empty. Clearing browser data removes the saved record. If browser storage is unavailable, the clock can still be used during the current page session while the page clearly says that it cannot retain history.

The boundary is intentional. This is a personal local practice clock, not FIDE-certified hardware, a tournament record, a game result service, a chessboard, a move recorder, or an arbiter workflow. Tournament rules, time controls, clock certification, flag claims, and corrections are controlled by the event. Use this tool when a clear two-sided clock with a documented Fischer increment is the useful part. Set the time control before starting, press after each move, pause when the practice game stops, use Undo for a mistaken press, and export only the private daily history you choose to keep.

Methodology & sources

Chess Clock stores a bounded local snapshot under counter:chess-clock. The snapshot has two mutually exclusive timers, an active side, a Fischer increment, and a timestamp anchor. The selected model follows FIDE Equipment 3.3.3 (increment before move one) and Laws 6.2.1 (the press stops the mover and starts the opponent). Every completed press records a device-local calendar-day count; undo restores the full prior snapshot and removes that count. It intentionally excludes delay, move records, official certification, and tournament administration.

Frequently asked questions

Does this implement Fischer increment or delay?
It implements Fischer increment only: the increment is shown before move one and credited to the player who completes a clock press. Delay is a different time-control mode.
What happens when time reaches zero?
The clock marks that side as flagged and stops accepting new clock presses until you set a new local time control.
Is this an official tournament clock?
No. It is a local practice aid, not certified hardware, a move record, an arbiter tool, or an official tournament result.

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