Fill the 9×9 grid so every row, column and 3×3 box holds the digits 1 to 9 exactly once.
Work box by box hunting hidden singles, and track candidates mentally for rows and columns that are nearly complete. Never guess: every hard grid yields to logic.
When stuck, re-scan the digits that appear most often — they usually hide the next deduction. Fresh eyes on the same grid find what tired eyes missed.
Yes, completely free in your browser, no download and no registration.
Hard: fewer clues than standard grids, requiring candidate elimination and deeper deduction chains.
No. Every daily grid is solvable by pure logic — patience is the only requirement.
Yes, a fresh hard grid is published every day.
Sudoku Difícil is the daily sudoku for players who like their logic with teeth. Every morning it publishes a fresh hard 9×9 grid with noticeably fewer starting clues, and that scarcity changes everything: you can no longer coast on obvious singles, and every digit must be earned through candidate elimination, hidden pairs and patient cross-referencing. There are moments where the grid seems frozen and the next move invisible, and the reward comes when a chain of deductions suddenly unlocks five cells at once. The rules are the pure classics: every row, column and 3×3 box contains 1 to 9 exactly once, and every grid is solvable by logic alone. Given numbers stand apart visually, conflicts are flagged instantly, and the number pad works under mouse or fingertip. Hard sudoku occupies a special place in every solver's journey: it is where the game stops being casual and starts being a craft. Techniques that sound exotic in theory — naked pairs, pointing pairs, box-line reduction — become daily tools at this level, and mastering them is genuinely satisfying. The daily format gives you a fresh arena every morning to practice under real conditions. When you finally crack a hard grid without a single mistake, the sense of accomplishment keeps you coming back, day after day.