A sudoku app that teaches

Learn why a move works,
not just where it goes.

Ask for help in small doses, see the reasoning drawn on the grid, and practise one technique at a time on puzzles built for it.

Coming soon to the App Store

For iPhone and iPad · No account, no ads, no tracking

Help in doses

Start with Where?, the mildest nudge. Only ask for Which cells? and Why? if you still need them.

See the reasoning

A solid outline for the pattern, a dashed one and a struck-through digit for what can go. Step by step walks a chain one link at a time.

Practise one technique

Read how it works, then solve a puzzle that needs it. From Naked Singles to Jellyfish.

Everything in one place

Your own notes, your own pace

A grey row for notes, a blue row for numbers. Mark only the digits that have two or three places left, the way Snyder notation works, and let the grid show you the patterns.

Your own notes, your own pace

Know what to look for

Tap Hint and the panel lists every technique that has a hit right now, with a count. It answers “what can I do here?” without giving the move away.

Know what to look for

Help in doses

Where? Which cells? Why? Apply. Take only as much help as you need, and see the reasoning drawn on the grid.

Help in doses

One technique at a time

Pick a technique, read how it works, then solve a puzzle that actually needs it. Two dozen techniques, from Naked Singles to Jellyfish.

One technique at a time

See what you really know

For every technique: how often you found it yourself, peeked at it, or took it from a hint. Stored on your device only.

See what you really know

Light, dark, and easy to read

It follows your phone, or you choose. Bigger numbers, highlighted rows, columns and boxes, all optional. Free for everyone.

Grid9 in the dark theme
Dark
Grid9 in the light theme with larger numbers
Light, with larger numbers

Learn Grid9

Five short guides, with the real screens and a clear note on what is free and what needs Premium.

Guide 1Solving routineHow I work through a puzzle, tool by tool, in the order that works for me.Guide 2Learning a strategyHow to pick up one unfamiliar technique on purpose, using practice mode.Guide 3App featuresEvery part of the screen and the menu, and what it does.Guide 4Custom puzzlesType in a puzzle from paper or another app and use every tool on it.Guide 5StatisticsWhat the app tracks, what the numbers mean, and where they live.

From the developer

Why I made Grid9

“I thought of an app that could help you, but in levels: a small first nudge in the right direction. If that is not enough, you can get one more hint.”

— Joachim Hagedorn

Read the story →

Try it yourself

Coming soon to the App Store

Free to play. Premium unlocks the hint steps, practice runs and custom puzzles, with a free trial for new subscribers.