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Today's puzzle

Medium Sudoku — Play Free Online

Free medium Sudoku puzzles, playable in the browser with no sign-up. Around 34 clues to start, and the first level where pure scanning runs out before the grid does — you will need to think about where a digit can go in a unit, not just what can go in a square.

Clues to start
about 34
Par time
12 min
Cost
free, no sign-up

What changes at this level

Medium grids open like easy ones. A dozen squares fall quickly, and then the board goes quiet: you sweep all nine digits, find nothing, and sweep again. That silence is the level working as designed, not a sign you have made a mistake.

What breaks it is a change of question. Instead of asking what can go in a square, you ask where a given digit can go in a given row, column or box. Often the answer is one place, even though that square could have accepted two or three other digits. That is a hidden single, and it is the technique this level is built around.

The most-played level

Medium is where most people settle, and it is the default the board starts on. It is long enough to feel like a puzzle and short enough to finish in one sitting — the par time here is 12 minutes, and beating it earns a speed bonus on your final score.

This is also the level where pencil notes start earning their keep, though not everywhere at once. The medium guide covers how to use them on one unit at a time instead of filling in the whole grid.

If it feels too hard, or too slow

Stalling repeatedly usually means hidden singles have not clicked yet, not that you need a gentler puzzle — spend a few grids on easy Sudoku to get the scanning automatic, then come back. If instead you are finishing without ever getting stuck, go straight to hard Sudoku.

Scoring, and why slow often beats fast

A medium finish is worth 250 points, and each second under the 12-minute par is worth 1.5. So two minutes saved is worth about 180 points — and a single mistake costs 50, a hint 75.

Those numbers are deliberately set so that a careful solve beats a rushed one. Rushing a medium grid tends to produce exactly the error the level invites: entering a digit that fits the square you are looking at without checking whether the unit had somewhere else to put it.

What to practise here

One thing, until it is automatic: turning the question round. When scanning stalls, stop asking what goes in a square and start asking where a digit can go. Pick a box, list the digits it is missing, and take them one at a time.

Players who find medium frustrating are nearly always still asking the easy-level question and concluding the grid is unfair when it stops answering. Players who find it too easy have usually internalised the medium question already and should move to hard, where the question changes again — from placing digits to eliminating them.

Common questions

What makes a medium Sudoku harder than an easy one?

Not the number of clues on its own, though there are fewer — around 34 rather than 42. What changes is that scanning runs out before the grid does. A medium puzzle reaches positions where no square can be resolved by looking at it, and the next move has to come from asking where a digit can go in a unit rather than what can go in a square.

Why do I keep getting stuck on medium Sudoku?

Almost always because hidden singles have not clicked yet. Take one box and one digit it is missing, then check its empty squares one at a time and discard the ones whose row or column already has that digit. If one square survives, the digit goes there — even if that square could still have accepted three other digits. That is the move the level is built around.

How long should a medium Sudoku take?

Twelve minutes is the par time for the speed bonus. A comfortable solve usually lands between eight and twenty. If you are regularly over half an hour it is normally one specific technique missing rather than general slowness, and if you never get stuck at all you are ready for hard.

Do I need pencil marks at this level?

Not across the whole grid. Medium puzzles are solvable without writing anything down, and learning to find hidden singles in your head is the training that makes the harder levels workable. If you do stall for several minutes, annotate a single unit rather than the whole board — that is almost always enough.

Does a medium Sudoku ever require guessing?

No. Every puzzle on this site has exactly one solution and can be reached entirely by deduction. A position that appears to need a guess is a position with a deduction you have not spotted — usually a hidden single, occasionally a pair. Guessing can only cost you, because a wrong digit poisons every note you write after it.

Other levels