How to solve Sudoku: tips & techniques
Once you know the rules, solving faster is about spotting patterns. Here's a path from basic logic to advanced techniques.
Start here: singles
The two most useful beginner techniques are naked singles and hidden singles. A naked single is a cell that has only one possible candidate left, once you rule out every digit already used in its row, column and box. A hidden single is a digit that can only go in one cell within a row, column or box, even though that cell may still show other candidates. Scanning for both after every move is the fastest way to make steady progress. Turn on Notes while you play to track candidates as you go.
Pointing pairs and pairs
When a candidate digit inside one 3×3 box is restricted to a single row or column within that box, it can be eliminated from the rest of that row or column outside the box — this is a pointing pair. A naked pair is two cells in the same row, column or box that share the exact same two candidates; those two digits can then be removed as candidates from every other cell in that unit.
Advanced: X-Wing and beyond
An X-Wing pattern appears when a candidate digit is restricted to exactly two cells in each of two different rows, and those cells line up in the same two columns. That lets you eliminate the digit as a candidate from the rest of those columns. Related patterns like Swordfish extend the same idea across three rows or columns. These techniques take practice to spot, but they're what let you push through the hardest puzzles without guessing.
Killer Sudoku: cage combinations
In Killer Sudoku, start with the smallest cages — a two-cell cage with a low or high target sum often has only one or two possible digit combinations. Sudokumee's built-in cage helper shows the live valid combinations for the cage you've selected, so you can narrow candidates down without doing the addition by hand.
Stuck on a specific move?
If you're playing on Sudokumee, the in-game Hint button explains the logic behind your next move — naming the technique it used — rather than just filling the answer in for you. See the full rules on the how to play page, or jump into a puzzle now.
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