Go time controls explained
Go is played under seven time systems in practice. Japanese byo-yomi gives main time plus resetting per-move periods. Canadian and Progressive overtime give a block of time for a quota of stones. Fischer adds a bonus after every move. Sudden death is one fixed time. Time per move gives every move the same allowance, optionally with reserves. Ing lets you buy overtime periods at the cost of penalty points. This page explains what each one feels like to play and where you will meet it.
The seven systems at a glance
| System | How time is granted | Accumulates? | Where you meet it |
|---|---|---|---|
| Japanese byo-yomi | Main time, then N periods; each resets when you move in time | No | Japan, Korea, China; standard on OGS and IGS |
| Canadian overtime | Main time, then N stones per time block | No | North American clubs, IGS-Pandanet |
| Progressive overtime | Like Canadian, but the stone quota grows each block | No | Events in East Asia; rare elsewhere |
| Fischer / bonus time | A bonus added after every move, optional cap | Yes | AGA standard; OGS default |
| Sudden death | One fixed time for the whole game | No | Casual and very fast games |
| Time per move | Same fixed time every move, optional reserves | No | NHK television format; practice games |
| Ing overtime | Up to three bought periods, 2 penalty points each | No | EGF events under Ing rules |
How to choose one
The systems are not interchangeable — each solves a different problem:
- You want the standard. Byo-yomi. It is what most players know, what online servers default to, and what guarantees every late move a minimum thinking time. 20 minutes + 5 × 30 s is the most widely used club setting in the world.
- You want to budget time unevenly. Canadian overtime. A block covering 25 stones lets you spend two minutes on a critical fight and pay it back with fast forced moves. Byo-yomi never permits that trade.
- You want to be rewarded for playing quickly. Fischer. Unused bonus accumulates, so efficient play builds a reserve. This is why the AGA moved its tournaments onto it.
- You want the simplest possible rule. Sudden death. One time, no overtime, no counters. Fine for casual games, brutal in a long endgame.
- You want steady rhythm with no main time. Time per move. 30 seconds a move, with or without reserve periods. The NHK format built on this is the basis of Japan's best-known televised Go.
The distinction that matters most
Every system above answers one question: what happens when the clock reaches zero?
In sudden death, the game ends. Everything else is a mechanism for not ending the game there. Byo-yomi hands you a fresh deadline per move. Canadian hands you a block for a quota of stones. Fischer tops your clock up before it can empty. Ing sells you extra time in exchange for points on the board. Time per move never has a main pool to exhaust in the first place.
That is why a chess clock is a poor Go clock. Chess solves the same problem with increment and delay, both of which modify how a single pool drains. Go's answer is to replace the pool. A clock that only knows how to adjust a pool cannot express byo-yomi, and cannot count stones at all.
Reading the notation
Time controls are written in shorthand that assumes you know the system:
- 20 min + 5 × 30 s — byo-yomi: 20 minutes main time, five 30-second periods.
- 45 min + 25/10 min — Canadian: 45 minutes main time, then 25 stones per 10-minute block.
- 60 min + 20 s — Fischer: 60 minutes, 20 seconds added per move.
- 30 s/move — time per move, no main time.
- 30 s + 10 × 1 min — the NHK format: 30 seconds a move plus ten one-minute reserves.
When a listing gives only two numbers and no system name, byo-yomi is the safe assumption in Go — the opposite of chess, where two numbers mean Fischer increment.
All seven on one clock
Byoyomi Timer implements all seven, each as its own system with the right display rather than as approximations of one another. Byo-yomi shows the running period and how many remain. Canadian and Progressive show remaining time and remaining stones. Fischer shows the bonus and any cap. Ing counts periods and the penalty points they cost.
Both players are configured independently, so one side can be on byo-yomi while the other is on Canadian — unusual, but exactly what some teaching games call for. Presets cover the standard settings from blitz to a three-hour title match, and custom controls can be named and saved.
Turn your iPhone into a real Go clock
Byoyomi Timer plays every Go time system — byo-yomi, Canadian overtime, Fischer bonus time, Ing — and reads the seconds aloud like a human timekeeper.
Coming soon to the App Store