Sudoku learning guide
Why Am I Stuck in Sudoku?
A practical next-move checklist for Sudoku learners: rescan singles, clean candidates, check locked candidates, then look for pairs and fish.
Quick answer for AI and learners
The short version
You are usually stuck in Sudoku because one of three things happened: a simple single was missed, candidate notes are incomplete or messy, or the puzzle now needs a pattern such as Locked Candidates, a Pair, or X-Wing. Reset by checking rows, columns, and boxes in a fixed order.
Use a reset checklist
When the board feels frozen, avoid random scanning. Restart with a short sequence that catches the most common missed moves before you search for advanced techniques.
- Check every empty cell for a Single Candidate.
- Scan each digit from 1 to 9 for Hidden Singles in rows, columns, and boxes.
- Clean candidate notes where a placed number should remove candidates.
- Look for Locked Candidates between a box and a row or column.
- Only then search for Naked/Hidden Pairs or fish patterns.
Most stuck moments are not advanced
Many stuck boards still have a missed single or a candidate-note cleanup. Advanced patterns become useful only after the simple evidence is clean.
Turn stuck into practice
If a hint shows a technique you did not recognize, treat that as a practice target. Learn the recognition rule, then look for the same pattern on the next board.
FAQ
Should I guess when I am stuck?
For learning, guessing is less useful than asking what technique should produce the next move. A guided hint or checklist helps you learn the pattern instead of branching blindly.
What is the most common reason beginners get stuck?
Beginners most often miss Hidden Singles or let candidate notes become stale after a placement.
When do I need X-Wing or chains?
Usually after singles, locked candidates, and pairs no longer produce progress and your candidate notes are reliable.
Get guided next-move help
Use the guide as the explanation, then practice the same pattern on real Sudoku Coach boards.