How to Solve Your First Sudoku, Step by Step

Step 1: take a slow look before touching anything

Before you place a single value, scan the whole board slowly. Notice which rows, columns and boxes already hold a lot of values, because those crowded areas are where the easy moves hide. A group that is nearly full has very few possibilities left, so it gives up its answers with the least effort. Starting where the board is fullest is the single best habit a beginner can build, and it keeps you from feeling overwhelmed by the empty spaces.

Step 2: find a group with a single gap

Hunt for any row, column or box that already has eight values placed and just one empty cell. Whatever value is missing is forced into that gap, because the group must contain all nine exactly once. This is the safest move in the entire game, and every time you make one, the board becomes a little easier for the next move. Keep circling back to look for new single gaps as you fill things in.

Step 3: pick a value and chase it through the boxes

Now choose one value and look at a single box. Ask where that value can legally go inside the box, and skip any cell that already sees the value somewhere in its row or column. If only one cell survives that test, the value belongs there. Work the same value across the other boxes before moving on to the next value. This scanning habit, sometimes called cross hatching, is where most of your early progress will come from.

A worked example with coordinates

Say you are placing the circle shape and you look at the top left box, which spans r1c1 to r3c3. The circle already appears in row 2 at r2c8 and in column 1 at r7c1. That rules out every cell in row 2 of the box and every cell in column 1 of the box. If the box also already has shapes in r1c2 and r3c3, you may find that only r1c3 is left open for the circle. Because it is the one surviving cell, the circle is forced into r1c3. Notice that you never guessed. You simply removed every illegal option until a single legal one remained.

Step 4: switch on notes when it gets harder

When the obvious moves run out, turn on Notes mode and mark the candidate values for each empty cell. Writing the possibilities down turns a confusing board into a clear one. A cell that ends up with only a single candidate is solved, and a value that fits only one cell in a group belongs to that cell even if the cell could in theory hold others. Notes are not cheating; they are simply how experienced solvers think.

Step 5: keep your notes honest

Every time you place a value, it instantly becomes impossible everywhere else in that same row, column and box. Remove it from those notes so you never chase an option that no longer exists. Shapedoku can do this cleanup for you automatically with Smart Notes Cleanup, which spares beginners the most common early mistake of acting on a candidate that has quietly gone stale.

Step 6: slow down when you stall

If you get stuck, resist the urge to guess. Refill your notes, pick one group, and study it closely, because the next move is almost always hiding in plain sight. If you genuinely cannot find it, a single hint will reveal one correct cell and often restarts your momentum. In Shapedoku the first hint of each puzzle is free, and it can explain why the shape fits, so it doubles as a small lesson rather than just an answer.

A simple loop to remember

1. Scan for any group with a single empty cell and fill it.
2. Pick a value and place it wherever it is forced inside a box.
3. Turn on notes once the easy moves dry up.
4. Solve any cell that has only one candidate left.
5. Remove placed values from related notes and repeat until the grid is complete.

That loop will carry you through any Easy or Medium board without a single guess. Start gentle, trust the logic, and enjoy the quiet satisfaction of a finished grid. You can play your first puzzle right now in the browser at app.shapedoku.com, free and with no account, and the Beginner tier is built to make these first steps feel easy.