Sudoku Speed-Solving Tips

By Haroon Mustafa · Updated October 2026 · 4 min read

Fast sudoku solving isn't about guessing well — it's about spotting the same handful of patterns quickly and consistently. These five techniques cover most of what you need to move from a slow, guess-heavy approach to confident, methodical solving.

1. Scan rows, columns, and boxes together

Instead of scanning a single row for a missing number, cross-reference the row, column, and 3x3 box at the same time. If a number is already present in any of the three, that cell can be ruled out immediately — this alone eliminates most of the guesswork for easy and medium puzzles.

2. Use pencil marks early, not as a last resort

Many solvers only add candidate numbers when they're stuck. Doing it from the start — noting every possible number in a cell before you commit to one — actually saves time overall, because it surfaces "naked singles" (cells with only one possible number) much faster than scanning alone.

3. Look for hidden singles

A hidden single is a number that can only go in one cell within a row, column, or box, even if that cell has other candidates written in. These are easy to miss visually but are one of the fastest ways to fill in cells once you know to look for them.

4. Master pairs and triples

When two cells in the same row, column, or box share exactly the same two candidate numbers, those two numbers can be eliminated from every other cell in that group. The same logic extends to triples. This technique unlocks most "medium" and "hard" puzzles that scanning alone can't crack.

5. Work the puzzle in passes, not cell-by-cell

Rather than trying to fully solve one cell before moving to the next, make a full pass through every row and box looking only for one pattern (like hidden singles), then a second pass looking for another (like pairs). This keeps your brain focused on one type of pattern at a time, which is faster than context-switching cell by cell.

A worked example: finding a hidden single

Look at one 3×3 box and pick a number that is missing from it, say 7. Now check the rows and columns that pass through the box. If there is already a 7 in two of the three rows and two of the three columns, the 7 in this box can only go in one square. That is a hidden single. You did not need to know what else goes in that square; you only needed to know where the 7 cannot go. Doing this for every number in every box is the fastest way through Easy and Medium puzzles.

Using notes in Playnook's Sudoku

Notes (pencil marks) let you write small candidate numbers in a square. On Easy you rarely need them. On Hard and Expert you will. A good routine is to solve everything you can by scanning, then fill in notes for the remaining squares in one box or row at a time. When you place a number, remove it from the notes in the same row, column and box. The conflict highlighting helps you spot when two of the same number end up in one line.

Naked pairs in plain words

If two squares in the same row each have only the same two candidates, for example 3 and 8, then those two numbers must go in those two squares. That means 3 and 8 cannot go anywhere else in that row, so you can remove them from the notes of every other square in the row. This one idea often breaks a Hard puzzle open.

Common mistakes

The biggest is guessing. Sudoku puzzles are made to be solved by logic, and a guess that turns out wrong can ruin the whole grid before you notice. The second is forgetting to update notes after placing a number. Out-of-date notes lead to wrong answers. The third is staying on one stuck area too long. If a box is not giving you anything, move to a different number or a different part of the grid and come back later.

Getting faster

Speed comes from habits, not hurry. Scan numbers in order, 1 to 9, every time. Finish easy wins before reaching for notes. Time a few Easy puzzles and try to beat your best, then move up a level once your times settle down.