Verified hard Sudoku
Play Hard Sudoku Online
Choose from three calibrated hard puzzles. New Game stays on Hard, and the Puzzle ID, difficulty score, and solving facts update with the board.
Hard · LDI v0
Your current hard puzzle
LDI v0
Verified puzzle facts
- Puzzle ID
LDI0-01cb0dcea7b0ea68bf57e4634a750ff0d862017f- Difficulty model
- LDI v0
- LDI score (0–100)
- 31
- Clue count
- 27
- Logical steps
- 54
- Hardest technique
- Hidden Single
Clue count is a board fact, not the difficulty verdict. The tier comes from this published LDI version.
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Latest available daily challenge
Latest available Hard Sudoku challenge
Play this tier in the dated challenge collection available through August 15, 2026.
Why this tier
Hard is a calibrated result, not a label based on clue count.
The score reflects proof-checked techniques and logical steps. Clue count remains useful context, but it does not decide the tier by itself.