SudokuPrime
A REAL CHALLENGE

Hard Sudoku Puzzles

Free hard Sudoku with 30 clues. Take notes, look for pairs, and enjoy the breakthrough.

HARD LEVEL

A deeper challenge.

Hard 00:00Mistakes 0
Puzzle progress0%

1–9 to fill · Shift+1–9 for notes · Arrows to move · Delete to erase

◇ No account needed✓ Always free to play◎ Made for your focus
HARD SUDOKU

Where notes become essential

Only 30 clues to work with.
Patience pays off.

30 CLUES

Large empty regions

Hard puzzles start with 30 filled cells. Whole boxes can be nearly empty, so you will often need to reason across several units at once.

MIXED LOGIC

Singles, then more

Some Hard grids fall to singles alone if you spot every one. Others need a candidate technique such as a pointing pair or a naked pair to break open.

20 TO 40 MIN

A proper challenge

Plan on 20 to 40 minutes. Pause at any time: the timer stops and your grid stays saved in this browser.

TECHNIQUES FOR HARD

How to solve a hard Sudoku

Try it now ↗

  1. Fill in candidates

    Write every possible digit in the empty cells of one box or row at a time. Complete notes reveal patterns you cannot see otherwise.

  2. Pointing pairs

    If a digit's only spots inside a box are in the same row, that digit cannot appear anywhere else in that row. Remove it from the other cells of the row. The same works for columns.

  3. Naked pairs

    Two cells in the same unit that can only hold the same two digits, for example 4 and 7, lock those digits. Remove 4 and 7 from every other cell of that unit.

  4. Go back to singles

    Each elimination can create a new single. After every advanced step, scan again for naked and hidden singles before looking for the next pattern.

KEEP PLAYING

More free Sudoku puzzles

Daily SudokuOne shared puzzle a day.Easy Sudoku43 clues, perfect to start.Medium Sudoku36 clues, room to think.Expert SudokuAbout 25 clues, beyond singles.6×6 SudokuDigits 1 to 6, great for kids.Killer SudokuCages, sums, and pure logic.Sudoku SolverSolve any puzzle, step by step.Printable SudokuPrint or save as PDF.Sudoku StrategiesLearn every solving technique.
GOOD TO KNOW

A little clarity
before you play.

The details, without the distractions.

How hard is hard Sudoku?

Hard puzzles start with 30 clues. Many need careful scanning and notes, and some require a candidate technique such as a pointing pair or a naked pair.

What techniques do I need for hard Sudoku?

Naked and hidden singles, plus candidate notes. Pointing pairs and naked pairs are the most useful next steps.

Can I get a hint?

Yes. Hints are unlimited and fill one cell at a time. They are counted in your results.

Does the game save my progress?

Yes, when browser storage is available. Each difficulty and the Daily Sudoku keep their own saved game in this browser, so switching levels never erases your progress.

SUDOKU PRIME