Hard sudoku online
You land on a hard classic grid — same rules as easy or medium, just fewer free singles. Expect more pencil work; Hint names the next technique when you stall.
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Hard sudoku online
Hard sudoku uses the same rules as easy — it just stops handing you naked singles every other click. Expect more pencil work, more looking ahead, and occasional named techniques. This page loads a hard puzzle by default so a “sudoku hard” search does not land on a toy grid.
If the puzzle feels unfair, check conflicts with Check before blaming the generator — unique-solution hard grids can still be slow.
When
When to use
Medium feels automatic; you searched hard sudoku; you want a longer commute puzzle without jumping to evil.
When not
When not to
You are still learning placements → how to play or home on easy/medium. You want the meanest classic band → evil sudoku. You want cages → killer sudoku.
Defaults
Assumptions
Difficulty = generation settings (clue count + technique depth), not a marketing sticker. Still one solution. Timer (if shown) is local vanity, not a ranked ladder.
Steps
How
- Fill all naked/hidden singles before guessing.
- Keep Pencil candidates tidy — stale notes cause phantom blocks.
- When stuck, Hint once; read the technique; try to find the next one yourself.
- New puzzle stays in hard band.
Worked notes
Examples
- No cell has a single candidate, but a digit appears as a candidate only once in a box → place that hidden single
- Two cells in a unit share the same two candidates → naked pair; strip those digits from the rest of the unit
Watch-outs
Gotchas
- “Hard” on random sites sometimes means “ugly UI.” Here it means generation band.
- Clearing one hard puzzle does not mean the next is the same shape — seeds differ.
- Full-solution reveal trains nothing; prefer step hints.
Nearby pages
Compare
Meaner band: evil sudokuHabits: sudoku strategyRules: how to playHome default: home
Controls
Quick controls
- Hint — a cell/digit, technique name, and short reason.
- Check — flags conflicts without revealing the full grid.
- Pencil — candidate notes for empty cells.
- New puzzle — same difficulty band, fresh seed.
- Daily — fixed local seed for the calendar day.
- Erase — clear the selected cell (not givens).
FAQ
Common questions
Is hard different rules?
No — same 1–9 constraints; harder search.
Should I guess?
Last resort; candidates first.
Same hints as easy?
Same system; harder puzzles may cite deeper techniques.
Why a separate URL?
So “hard sudoku” lands on a board already in that band.