Beginner power move

Hidden Singles: The Fastest Way to Keep a Sudoku Grid Moving

A hidden single happens when a candidate only appears once inside a row, column, or box—even if the cell has other notes. Finding them early prevents guesswork and unlocks cascading placements. Use this guide plus the Pure Sudoku board to loop through hidden singles in minutes.

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Use smart notes that reveal hidden singles instantly.

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60% of medium wins start with a hidden single in Pure Sudoku
2 min Average time to clear a board once every single is spotted
100% Logic-based—no guessing needed on any board

How to spot a hidden single

  1. Pick a row, column, or 3×3 box and write every valid candidate.
  2. Count how many times each digit appears in that unit.
  3. If a digit only appears once, it must live in that cell—place it immediately.
  4. Update pencil marks around the placement so fresh singles surface.

Pure Sudoku highlights conflicts as soon as you type them, so you can enter candidate notes aggressively without worrying about mistakes. Need a clean slate? Open a fresh easy puzzle or launch an intermediate board for a bigger challenge.

Interactive play-by-play

Hidden single in action

Use the controls to see how a single digit hides inside a row and how quickly it locks into place.

Step 1

Fill the row with pencil marks

The middle row is packed with candidates, but only the center cell can still contain a 9.

Step 2

Spot the unique digit

Even though other notes exist, the 9 only appears once inside the unit. That makes it a hidden single.

Step 3

Place the value and clean notes

The 9 locks in, every conflicting note clears automatically, and the row is ready for the next scan.

Step 1 of 3

Hidden singles vs. naked singles

A naked single happens when a cell only has one candidate written in it. Hidden singles hide inside the unit—they may sit next to other notes, but that digit is unique inside the unit. Practicing both keeps your scan pattern sharp: sweep for naked singles inside cells, then evaluate each unit for hidden ones.

Try this 3-step drill

  1. Open an easy puzzle and fill every pencil mark for digits 1–4.
  2. Check each row for digits that appear once and make the placements.
  3. Repeat for columns, then boxes. Keep the loop running until the puzzle falls apart.

Want printable reps? Grab the worksheet pack and annotate each hidden single you find. Circling the digit you place helps you see patterns the next time around.

Level up from here

Once hidden singles feel automatic, stack them with:

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