What should I do first when starting a Sudoku?

Scan for hidden singles: pick a digit, see where it already appears, and look for a box where only one cell can still hold it. This fills in the easy placements quickly.

I am stuck on an easy puzzle — what now?

Switch between two checks: scan each digit for hidden singles, and inspect empty cells for naked singles (cells with only one legal digit left). One of them almost always yields the next move on an easy grid.

Your First Sudoku: A Walkthrough

A beginner-friendly walkthrough of solving your first Sudoku, from scanning for easy placements to filling the grid.

The fastest way to learn Sudoku is to solve one slowly, naming each move. This walkthrough takes you through the deductions a beginner uses on an easy puzzle — no advanced techniques, just scanning and the two kinds of "single" that solve most of an easy grid.

Try it on the practice grid below as you read: tap a cell, then enter the digit each step describes.

Start by scanning

Pick a digit, say 1, and look at where it already appears. Each existing 1 forbids that digit from the rest of its row, column and box. Run your eye along those lines (cross-hatching) and you will often find a box where only one cell can still hold the 1 — a hidden single. Place it, then repeat for the next digit.

Choose a digit and find every place it already sits.
Cross out its row, column and box across the grid.
If a box has only one legal cell left for that digit, place it.

Then look for naked singles

As the grid fills, some empty cells end up with only one digit that does not already appear in their row, column or box. That cell is a naked single — place the surviving digit. Alternating between hidden singles (scanning) and naked singles (checking individual cells) will carry you through any easy puzzle.

For an empty cell, list the digits not yet used in its row, column and box.
If exactly one digit remains, place it.
Each placement may create new singles — keep cycling.

Finish and check

Keep alternating between scanning for hidden singles and checking for naked singles until the grid is full. Then verify: scan each row, column and box once more for any repeated digit. If there are none, the puzzle is solved.

Try it yourself

Tap a cell, then a number, to practise.

Frequently asked questions

What should I do first when starting a Sudoku?: Scan for hidden singles: pick a digit, see where it already appears, and look for a box where only one cell can still hold it. This fills in the easy placements quickly.
I am stuck on an easy puzzle — what now?: Switch between two checks: scan each digit for hidden singles, and inspect empty cells for naked singles (cells with only one legal digit left). One of them almost always yields the next move on an easy grid.