Coffee Sudoku
Where Coffee Meets Numbers
Classic Sudoku, quiet interface
Three Hidden Modes
Unlock them by playing
Errors stay hidden, the mistake counter is gone, and you solve at your own pace. No scoring, no pressure.
Unlock by completing Very Hard mode once
Numbers vanish after 15 seconds, then every 20 seconds after that. You need to remember what disappeared. Think of it as Sudoku with a memory exam bolted on.
Unlock by winning Zen Mode once
The board starts empty. Instead of given digits, you get cages with target sums. No digit repeats inside a cage. It is a different kind of Sudoku that forces you to think about arithmetic and elimination at the same time.
Unlock by winning Redacted Mode once
Why Coffee Sudoku?
Completely Free
No ads, no purchases, no subscriptions.
Privacy First
No data collection. Your progress is stored locally on your device.
10 Languages
Play in English, Spanish, French, German, Italian, Portuguese, Romanian, Slovak, Japanese, or Polish.
Fully Accessible
Works with screen readers and other assistive tools.
Sudoku hub
Everything Sudoku in one place
A web board, rules, play routines, and technique guides. All on one site.
Play Sudoku online
A free web puzzle with classic, Zen, and Redacted modes.
Sudoku blog
Guides and strategies for playing faster and staying focused.
Learn the rules
The grid, the win condition, and what counts as a legal move.
Build a play routine
How to start a board, when to rescan, and how to use notes without cluttering the grid.
Basic techniques
Practice beginner techniques like naked singles, hidden singles, notes, and locked candidates.
Advanced techniques
Intermediate patterns with pointing, claiming, naked pairs, and hidden pairs.
Master techniques
Expert patterns: X-Wing, XY-Wing, Swordfish, and uniqueness logic.
Technique atlas
Every named Sudoku technique, grouped by family. Pick one family at a time.