Sudoku that works entirely on your device.
NineFold is a Sudoku game for iPhone and Android that works entirely on your device. There is no account, no login and no server, so most of what a support page usually has to explain does not apply here: there is nothing to sign in to, nothing to sync, and nothing held anywhere else.
NineFold Pro is a one-time purchase. It removes the ads and lifts the daily hint allowance, and because it is not a subscription it cannot lapse.
If you have bought it before — on a new phone, after reinstalling, or after signing back in — open Settings → NineFold Pro, then tap Restore purchase on the screen that opens. The app asks the App Store or Google Play whether the account you are signed in to owns it, and unlocks Pro if it does. Two things are worth knowing:
If Restore purchase finds nothing and you believe it should have, your store’s own purchase history is the place to look first — that record is exactly what the app is asking about.
Your games live in the app’s own storage on the device. Deleting the app deletes them, and there is no backup on our side to restore from, because nothing is ever sent to us in the first place. That is the trade for a game that needs no account and no connection.
One caveat on very long games: reopening the app restores your board and your pencil marks exactly, but the undo history it can bring back is capped at 300 moves. A game longer than that comes back with the board intact and the undo history cleared — the board is never wrong, you simply cannot step backwards through it any more.
A hint fills in the next digit on one tap. When the next solving step only rules candidates out rather than placing a digit, the hint names the technique and shows you the pattern instead. Every hint is justified by a real technique, never a guess: puzzles NineFold’s own technique solver cannot finish are never shipped in the first place.
The free version gives five hints a day, and you can earn up to five more by choosing to watch a short video. The allowance resets on a new day, and unused hints do not carry over to the next one. NineFold Pro lifts the limit and never offers you a video.
Running out of hints never blocks anything. Every puzzle is still completable — you are simply not told the next move. There are no lives and no refill timer.
The free version shows ads. NineFold Pro removes them entirely.
Where Google’s consent form for personalised ads is shown in your region, it appears before the app requests any ad, and a Privacy choices row under Settings → Privacy reopens it, so you can change your answer at any time. That row is present whenever there is a form behind it to reopen.
On iPhone, iOS asks separately whether NineFold may track you across other apps. Declining changes nothing about the game — you still see ads, they are simply less relevant.
The privacy policy is the full account of what does and does not happen to information about you.
The colourblind-safe palettes, the screen-reader support and the large-text support are free, and always will be — nothing that helps you read the board is behind a purchase. The palettes are under Settings → Theme.
admin@ninefoldhq.com
Support is one person, so a reply can take a few days. If something has gone wrong, the phone and the iOS or Android version it is running, plus what you were doing at the time, are the details that help most.