Easy Sudoku is the entry point to the standard 9×9 rules: right for a first game, and right for anyone who wants a light bit of logic. There are plenty of givens and plenty of empty cells, so almost every step can be spotted straight off the grid — no long candidate lists, and no guessing.
How to play easy Sudoku
There is only one job here: find the digits that are already certain. Start from the rows, columns and 3×3 boxes that already hold the most numbers:
Scan a full-ish row, column or 3×3 box and note which digits are still missing.
Cross out impossible spots using the row, column and box that cut through them.
When a cell has only one candidate left, write it in (a naked single).
When a digit has only one spot left inside a unit, write it in too (a hidden single).
Re-scan after every digit — one answer usually leads straight to the next.
This level rarely needs heavy note-taking: pencil in candidates only when you stall, and never guess.
FAQ
Is easy Sudoku good for beginners?
Yes. It leans on basic scanning, single candidates and hidden singles, which is the gentlest way into standard Sudoku.
What if I get stuck?
Go back to the row or box with the most digits filled — the answer is usually right next to something you already wrote. If you truly cannot see the next step, spend one hint: it names the cell and explains why.
What is medium Sudoku?
Medium Sudoku is for players who know the rules and want to step up from easy. It still follows the standard 9×9 rules, but fewer digits can be spotted at a glance, so candidates have to be written down and compared. Beyond single candidates and hidden singles you will use locked candidates, naked and hidden pairs, and box-line interaction.
Compared with easy boards, medium ones leave more room to think, without the dense multi-step chains that hard boards demand.
How to play medium Sudoku
Play with candidates on purpose. Fill every solid single first, then use local relationships to shrink what is left:
Finish the basic scanning, naked singles and hidden singles you used on easy boards.
Pencil candidates into the cells that are still open, and keep them current after every digit.
Compare a 3×3 box with the rows and columns crossing it to find locked candidates.
Check whether two digits are confined to two cells inside a unit (a naked or hidden pair).
After every elimination, immediately re-check the affected row, column and box for new singles.
The goal at this level is managing candidates accurately in one part of the grid. Once short-range elimination feels automatic, move up to hard.
FAQ
Is medium Sudoku hard?
It asks for more candidate work than easy, but usually moves forward more easily than hard. Basic scanning, locked candidates and pairs are often enough to make progress.
Do I have to take notes?
Not required, but strongly recommended. Press the Notes button, then tap digits to pencil candidates into a cell; the notes clear themselves as soon as the digit is placed.
Where is hard Sudoku hard?
Hard Sudoku is for players who finish medium boards reliably. It wants a fuller candidate grid and longer chains of elimination. Far fewer digits go in straight away, and candidate relationships across several rows, columns and 3×3 boxes usually have to be read together. Locked candidates, naked and hidden pairs and some triples can arrive back to back, and one correct elimination often means re-scanning the whole grid before the next single appears.
It is not where a beginner should start, and it is not a guessing game either: with complete notes and a trail you can follow, every step is derivable.
How to play hard Sudoku
The job here is tracking how one elimination reaches several connected units:
Fill every reliable single, then build a complete, current candidate map for what is left.
Follow candidates along rows, columns and boxes instead of staring at a single unit.
Use locked candidates and box-line interaction to pass a restriction from one unit to another.
When cells are tightly linked, check naked pairs, hidden pairs, naked triples and hidden triples.
After each round of elimination, drop back to the simplest technique and re-scan — that usually gets things moving.
Compared with medium, a hard board may need several linked eliminations before a single digit is confirmed. Keep the reasoning visible in your notes, and save hints for when the next link really is invisible.
FAQ
How hard is hard Sudoku?
It needs fuller candidate notes and more coherent multi-step elimination than medium, aimed at experienced players — but it stays inside pure logic, with no trial and error.
Can I use hints on hard?
Yes, three per round. A hint tells you which technique applies, which cell it lands on and why it holds, instead of just handing you a digit.
What makes expert Sudoku different?
Expert Sudoku is for players who finish hard boards comfortably. The rules are still 9×9, but basic singles show up far less often, candidate relationships are denser, and several techniques usually have to work together. Beyond locked candidates, naked and hidden pairs you may need naked triples, hidden triples and deeper box-line interaction, re-checking the basics after every elimination.
How to play expert Sudoku
Expert boards test your judgement about which candidate pattern opens the position, and whether you can chain techniques in the right order:
Keep the candidate grid complete, and make sure every earlier elimination reached all affected cells.
Find the units and digits with the most restricted candidates first, then check the whole grid with intent.
Verify locked candidates, naked and hidden pairs and triples under their strict conditions — do not strip candidates early.
Watch whether one technique’s elimination happens to create the exact conditions for another.
Remove candidates only once the full pattern holds, then go back to the simplest technique and re-scan.
Compared with hard boards, expert ones lean on pattern choice and technique combinations rather than a longer version of the same scan. A hint can point out the step you missed, but understanding why the pattern holds is what actually clears the level.
FAQ
What is the difference between expert and hard?
Expert boards offer fewer direct placements, demand longer and denser candidate analysis, and combine advanced elimination techniques more often.
Does expert Sudoku still need notes?
Yes. Candidate notes are how you track relationships across rows, columns and boxes, and expert boards are almost impossible without them.
Online Sudoku: four levels mapped to four ways of thinking — easy runs on basic scanning and single candidates, medium adds locked candidates and pairs, hard needs multi-step elimination, expert chains techniques together. A timer, candidate notes, undo and three free hints per round; works on phone and desktop, no sign-up.
How to play
Fill 1–9 into the 9×9 grid so that every row, every column and each 3×3 box (the thick lines) contains 1–9 exactly once. Tap an empty cell, then tap a digit on the keypad. The bold light digits are the puzzle’s givens and cannot be changed.
Four levels
Easy only needs basic scanning and single candidates; medium wants notes, locked candidates and pairs; hard needs multi-step elimination; expert chains several techniques together. The write-up for each level sits under the board and switches with it.
Tools
Undo steps back; Erase clears the selected cell; Notes switches to candidate mode, where a digit pencils a small mark instead of an answer; Hint gives three per round and says which technique applies, which cell it lands on and why it holds.
Timer and reset
The clock starts with the board and stops when the grid is full. Switching difficulty resets progress, the clock and your hints, then deals a brand-new board; New game deals again at the current level.
About this tool
Online Sudoku with four graded levels, a timer, candidate notes, undo and three hints per round. Pure front-end, puzzles generated in your browser, fine on phone and desktop.