Sudoku for absolute beginners
This guide is written for one specific person: someone who has opened a Sudoku a few times, filled in six or seven digits, felt the grid go quiet, and closed it again. That experience is so common that many people conclude the puzzle needs a kind of mind they do not have. It does not. Almost everyone who stalls out is stalling for the same two reasons — they are searching the grid in the least productive direction, and at some point they wrote down a digit they were not sure about.
Fix those two things and a beginner grid becomes a slow but steady walk to the end. The goal here is narrow and practical: your first Sudoku finished by yourself, without revealing anything, on the Easy setting of our grid.
One rule, kept in three places
Sudoku has a single rule, and the reason it feels like more is that the rule is enforced in three overlapping places at once. Every row of nine cells must end up holding the digits 1 through 9, each exactly once. Every column must too. And every one of the nine heavy-bordered 3×3 blocks — we will call them boxes — must too.
Notice what this does not say. It says nothing about sums, sequences, diagonals, or which digit is larger than which. There is no arithmetic anywhere in Sudoku. If every 1 on the board were a circle and every 2 a square, the puzzle would be exactly as hard and exactly as solvable. Beginners who assume a hidden numerical trick spend their first grid looking for something that is not there.
The practical consequence of one rule in three places is this: every cell you look at belongs to a row, a column and a box simultaneously, so every digit already written blocks that digit from twenty other cells. Solving is nothing but reading those blocks carefully.
Hunt the digit, not the cell
Here is the habit that separates people who finish grids from people who stall. The natural way to approach an empty cell is to stare at it and ask, "what could go here?" — which means checking nine digits against three units, and usually ending up with four or five possibilities and nothing to write. Do that cell by cell across sixty empty cells and the puzzle feels like arithmetic homework.
Turn the question around. Pick a digit, hold it in your head, and ask where that digit is still allowed to live. You are now carrying one thing instead of nine, and the answer is often a single cell.
Take the three boxes across the top of a grid. Suppose the 4s are placed like this, with a dot for every cell we do not care about:
c1 c2 c3 │ c4 c5 c6 │ c7 c8 c9
r1 · · · │ 4 · · │ · · ·
r2 · · · │ · · · │ · 4 ·
r3 · · · │ · · · │ · · ·
The top-left box must contain a 4 somewhere. Row 1 already has its 4, over in the middle box, so no cell of row 1 can take another one. Row 2 already has its 4 as well, in the right-hand box. Two of the three rows are spoken for, so the top-left box's 4 must sit in row 3 — one of r3c1, r3c2 or r3c3. Three cells instead of nine, from two seconds of looking.
Now finish the job by checking those three columns downward. If column 2 has a 4 anywhere below, r3c2 is out. If column 3 has one, r3c3 is out. Two eliminations and the digit is placed with certainty. On an Easy grid this happens constantly, and it is the entire technique you need for your first finished puzzle.
Work one digit all the way around the board before moving to the next. Take the 4, sweep the three horizontal bands of boxes, then the three vertical bands, then move to the 5. When a placement happens, stay on the same digit: writing a 4 changes what you know about the other 4s immediately, and it is cheaper to re-sweep the digit in your hand than to come back for it later.
Choosing where to start
A fresh grid offers no obvious entry point, and picking badly costs beginners several minutes of staring. Two quick counts solve it.
Count the digits. Before writing anything, run your eye over the givens and find which digit appears most often. If the grid was dealt with six 7s and two 3s, start with the 7s. Each existing 7 blocks an entire row, an entire column and an entire box for that digit, so the most common digit is the one whose remaining homes have already been narrowed the most.
Find the crowded unit. Look for a box, a row or a column with only two or three empty cells. A box holding six givens has only three digits missing and three places to put them, which is a much smaller question than the one the rest of the board is asking. These crowded units are where the first certain placements usually come from, and each one you complete feeds the sweep with new information.
Combine the two and the opening ten moves plan themselves: sweep the most common digit across the whole grid, then attack whichever unit that sweep has left with the fewest gaps.
The mistake that quietly ends first attempts
At some point a cell will look like it is probably a 6. Not certainly — probably. It is the only cell that feels remotely reasonable, the grid has been silent for two minutes, and writing something is more satisfying than writing nothing. This is the single most destructive move available to a beginner, and it deserves an explanation of exactly why.
A written digit is not just an entry, it is a claim that gets used. Every deduction you make afterwards leans on it. Ten placements later, the grid is a mixture of things you proved and things you inherited from a hunch, and there is no visible difference between the two. When the contradiction finally appears — two 8s in a column, or a box with no room left for a 5 — the error is not where the contradiction is. It is wherever the guess was, and you have no way to find it by looking.
Our board helps, but only halfway, and it is important to know which half. If your entry repeats a digit that already exists in the same row, column or box, both cells are marked as conflicting the moment you type. That catches the crude mistakes instantly. What it cannot catch is a wrong digit that happens not to repeat anything yet — perfectly legal-looking, quietly incompatible with the one true solution, and it will not announce itself for another dozen moves.
So the discipline is simple, and it is worth more than any technique: write only what you have proved. If a cell is a 6 or a 9 and you cannot tell which, leave it empty and go somewhere else. There is always somewhere else — on an Easy grid there is always another cell that can be settled outright.
The three buttons, used the way they were meant to be
Our Sudoku board has four difficulties and three helper buttons, and beginners tend to either ignore them or lean on the wrong one.
- Check is your training wheel. It reports how many of your entries are wrong, without saying which. That is exactly the right amount of help: "everything you have entered is correct" tells you your reasoning is holding up, and a count above zero tells you to stop building and go back over what you wrote. Press it every ten or fifteen placements while you are learning.
- Clear my entries wipes what you typed and leaves the givens exactly as dealt. When Check reports two wrong entries in a half-finished grid, clearing and re-solving the same puzzle is usually faster than auditing, and the second run teaches far more than the audit would.
- Reveal solution asks you to confirm, then fills the whole grid and records no time. It exists for the evening when a puzzle has beaten you, and using it is not a moral failure — but on Easy, try Clear first. A grid you eventually cracked yourself is worth ten you watched being solved.
Three counters sit above the board. Empty counts the cells still blank and is the honest measure of progress. Time starts when you type your first digit, not when the page loads, so there is no penalty for sitting and reading the grid before you begin. Best is your own fastest time on that difficulty, kept in your browser and compared against nobody else.
One thing the board deliberately does not have is a notes or pencil-mark layer: each cell holds a single digit and nothing more. On Easy and Medium you will not miss it. If you reach Hard or Expert and want to track candidates, a scrap of paper beside the screen is faster than any on-screen note system we tried.
Timings we clocked solving these grids ourselves, so read them as estimates. A first Easy grid, solved deliberately with a sweep of every digit, takes most beginners somewhere around fifteen to twenty-five minutes. Once the digit-first habit settles in, that usually drops to four to eight minutes. Easy deals roughly 43 given digits, Medium about 36, Hard about 31 and Expert about 25; the exact count for your grid is announced when it is dealt, because the generator stops removing digits the moment a removal would allow a second valid answer.
When to stop, and how to restart well
Two stopping points are worth recognizing. The first is the honest pause: you have swept every digit once, nothing moved, and you are re-reading the same corner. That is not the end of the puzzle, it is the end of a pass. Go back to the crowded-unit count — pick the box with the fewest gaps and list, for each missing digit, how many cells in that box could hold it. If any digit has exactly one home, you have a placement, and one placement usually unlocks three more.
The second is the genuine dead end: Check reports wrong entries, or you have found a contradiction. Do not try to repair it cell by cell. Clear your entries, keep the same grid, and solve it again from the givens. The second attempt runs three or four times faster because you remember most of the early placements, and the mistake almost never repeats.
And if a session is simply not going well, close the tab. Every grid on this site has exactly one solution and it will still be solvable tomorrow. Sudoku rewards a rested twenty minutes far more than a stubborn hour.
What to carry into your second grid
Three habits, in the order they matter. Search for a digit rather than a cell. Write only what you have proved, and leave everything else blank. Start at the most crowded part of the board and let the openings spread out from there. Nothing else on that list needs a name, a chart or a technique glossary, and none of the more advanced Sudoku methods will make sense until these three are automatic.
When Easy starts feeling short, move to Medium and expect it to feel hard again for two or three grids — that is the level asking you to sweep more thoroughly rather than to learn anything new. If you want the same style of careful, contradiction-free reasoning in a different shape, Minesweeper and Pixel Logic are the two closest relatives on this site.
Questions beginners ask
Do I need to be good at math?
No. Nothing is ever added or compared in size. The nine digits are just nine symbols, and the whole puzzle is about noticing where a symbol cannot go.
Which difficulty should I start on?
Easy, at roughly 43 givens. It can be finished end to end by scanning for cells with only one possible digit, so it never demands a technique you have not read here.
Is pressing Check cheating?
No, and while you are learning it is the most useful button on the page. It tells you how many entries are wrong but never which ones, so it confirms your reasoning without solving anything for you.
Could a puzzle here have two different answers?
No. Each grid is verified to have exactly one solution before you see it, so any grid you are stuck on can be finished by reasoning alone.