The Go clock app, and what one needs to do
A Go clock app turns a phone into the two-sided timer a game of Go needs. The bar is higher than for a chess clock app: it has to implement byo-yomi periods that reset when you move in time, count stones for Canadian overtime, ideally speak the closing seconds, and let each player have entirely different settings. Most timer apps do one of these. This page explains what each requirement is for, so you can judge any Go clock — this one included.
The five things that actually matter
- Byo-yomi with true resetting periods. The test: complete a move inside the period and it must return to its full length without being consumed. If a move spends a period, or the period keeps draining, it is a delay mode wearing byo-yomi's name. See how byo-yomi works.
- A visible period count. Knowing you are in byo-yomi is useless without knowing whether two periods remain or five. This is a display requirement, and it is where phones beat segment-display hardware outright.
- A stone counter for Canadian overtime. The rule is defined by stones, not time alone, so the clock must track and show stones owed per player — and let you correct a miscount.
- A spoken countdown. Byo-yomi means "reading the seconds", after the official who read them aloud. When 30 seconds is your entire allowance, hearing the count without lifting your eyes from the board is the difference between playing and clock-watching.
- Independent clocks per player. Teaching and handicap games are normal in Go, and they need genuinely different settings per side — not one setting with an offset.
Why a phone, and where it is genuinely better
The honest case for a dedicated hardware clock is durability and the absence of distraction. The case for a phone is the display and the speaker.
A physical Go clock shows a handful of digits. It cannot show a running period, the number of periods left, a stone counter and the current time system all at once — it has nowhere to put them. A phone screen can, in type large enough to read across a goban, and it can change what it shows depending on the system in use. It can also talk, which no affordable clock does.
The drawbacks are real and worth naming: a phone can ring, lock, or run out of battery. A Go clock app has to answer all three, which is why Byoyomi Timer keeps the screen awake for the whole game, pauses cleanly if a call or app switch interrupts, and continues on the Lock Screen through a Live Activity.
What to be suspicious of
- "Byo-yomi supported" with no detail. Ask the reset question above. This is the most commonly misimplemented rule in the category.
- A chess app with a Go mode. Chess presets and Bullet/Blitz/Rapid vocabulary in a Go clock signal that Go was an afterthought — and it usually means no stone counter.
- Ads. A banner appearing during a two-hour game, or worse an interstitial when a period expires, is disqualifying in a way it would not be in a casual app.
- Requiring an account or a connection. A clock has nothing to sync. Many clubs meet in basements with no signal.
- No way to correct a mistake. Real games produce miscounts and mis-taps. A clock without referee tools forces a restart.
How this app is built against that list
Byoyomi Timer implements all seven systems Go is played under — Japanese byo-yomi, Canadian and Progressive overtime, Fischer bonus time with an optional cap, sudden death, time per move including the NHK reserve format, and Ing overtime — each with the display it needs rather than as a variation of one another.
The voice reads the last ten seconds of every period, the entry into byo-yomi, the final period and each lost period, in Japanese, Korean, Mandarin, English or German, independently of the interface language. Both clocks are fully independent. Time, periods and stones can be corrected mid-game. Pass buttons are built in, and two passes stop the clock for counting.
It has no account, no server, no analytics and no ads, works in airplane mode, and keeps time on the Lock Screen. The core clock is free; Pro adds custom systems, the tournament presets, teaching games, the additional themes, saved setups and history.
Free browser clock first
If you want to see whether phone-based timing suits your table before installing anything, the online Go clock on this site runs byo-yomi in the browser with no signup. It is deliberately limited — a browser tab can lock or be covered by a notification — but it is enough to try the idea at a real board.
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