Hard Sudoku
Advanced Sudoku with X-wing and chain techniques needed.
Hard Sudoku with ~28 starting clues. The same three rules apply — 1–9 in every row, column, and 3×3 box exactly once — but expect to need techniques beyond simple scanning: pointing pairs, naked pairs, and occasional X-wings.
Part of: Daily Challenges
Play first; notes and related practice are below
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How to use
- Rules: each of the 9 rows, 9 columns, and nine 3×3 boxes must contain every digit 1–9 exactly once.
- Tap a cell and press 1–9 (Backspace/Delete/0 to clear). Red means you violated a rule.
- Start with singles. When singles run out, look for pointing pairs: if a digit in a 3×3 box is only possible in cells sharing one row or column, it is eliminated from that row/column elsewhere.
- Every puzzle has one solution — no guessing required. If stuck, rescan each digit 1–9 across every row, column, and box.
- Your state saves automatically — take breaks and come back.
Examples
Hard difficulty
≈ 26 clues, typical solve 15–30 minutes.
Before you judge the score
Treat the score as feedback on one short practice round. It may reflect speed, attention, memory, or familiarity with the format, not overall ability.
The best next step is to review one missed pattern or one slow decision, then try a related practice or guide.
Next up
Frequently asked questions
› Do I need pen and paper?
Pencil-marks help at this level. They're on the roadmap for the app itself.
› Is every puzzle uniquely solvable? Trust & accuracy
Yes — the generator enforces a unique solution.
Tips & related reading
See the Daily Challenges hub →Tips & how-tos
- Sudoku Difficulty Explained
- The 15 Best Free Word Games on Kefiw
- Sudoku Difficulty Levels Explained
- A Daily Brain-Health Routine After 40
- Memory Changes After 40: What to Do Next
- Mental Math Practice With Calculators
- How Daily Word Challenges Work
- Daily Streak Tips
- Beginner Sudoku Strategy
- Brain Games for Seniors That Stay Fun Enough to Keep Doing