Byo-yomi vs Fischer time
Byo-yomi gives you a fresh fixed period for every move once your main time is gone; unused seconds never carry over. Fischer bonus time adds seconds after every move from move one, and unused seconds do carry over. In short: byo-yomi guarantees a minimum for every move no matter how badly you managed your main time, while Fischer rewards you for having played efficiently earlier.
Side by side
| Japanese byo-yomi | Fischer bonus time | |
|---|---|---|
| When time is granted | Per move, only after main time ends | After every move, starting at move one |
| Unused time | Discarded — the period resets to full | Banked — the clock can grow |
| Guaranteed per move | The full period, every move, forever | Only the bonus amount |
| Can you lose mid-game? | Only by overrunning your final period | Yes, whenever the clock hits zero |
| Typical notation | 20 min + 5 × 30 s | 60 min + 20 s |
| Game length | Can in principle run indefinitely | Trends downward; more predictable |
| Rewards | Consistency | Efficiency |
| Standard in | Japan, Korea, China; OGS, IGS | AGA tournaments; OGS default |
The same position, two systems
Imagine move 180. A complicated endgame sequence needs 90 seconds of reading. You have used your main time carelessly.
Under byo-yomi (5 × 30 s): you have a 30-second period. Ninety seconds of thinking costs you three periods; you complete the move in the fourth, which then resets. You have two periods left and can still play every remaining move with a full 30 seconds. Your earlier carelessness cost you nothing here — the system reset your account when main time ended.
Under Fischer (60 min + 20 s): you have whatever is on your clock. If you banked time early, you might have four minutes and the 90 seconds is comfortable. If you did not, you might have 25 seconds and the position is simply lost on time regardless of whether you can read it out.
That is the whole difference. Byo-yomi is forgiving of the past and strict about the present. Fischer is the reverse.
Which one to use
- Club evening, mixed strengths. Byo-yomi. Weaker players are not punished twice for thinking slowly early on, and nobody loses a nearly-finished game to a flag. 20 min + 5 × 30 s.
- Tournament on a schedule. Fischer has the practical edge: rounds finish nearer their planned length because the clock still trends down. This is the AGA's reasoning. 60 min + 20 s.
- Teaching game. Byo-yomi, with different period counts for each side — more periods for the student. The app allows fully independent settings per player.
- Online blitz. Either, but Fischer with a cap is common because it prevents both flag-losses and unbounded banking.
- Learning Go. Byo-yomi, because it is what you will meet everywhere else, and because the per-move deadline teaches you to read positions under a consistent constraint.
A note on mixing them
Nothing prevents the two players in a game from using different systems, and in Byoyomi Timer each side is configured independently. A strong player on Fischer against a beginner on byo-yomi is an unusual but perfectly coherent handicap: it gives the beginner a guaranteed floor per move while holding the stronger player to a budget.
What you should not do is switch systems mid-game. All of these rules depend on state — periods remaining, stones owed, banked seconds — and there is no meaningful conversion between them.
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