Palindrome Sudoku: rules, strategy and how to start
A palindrome line reads the same in both directions. The deduction is unusual: it does not tell you which digit is where, it tells you that two distant cells are equal.
Why the rule changes everything
Equal digits across two cells usually means those cells cannot share a unit — if both ends of a palindrome sit in the same row, the digit is impossible there and the line collapses.
That makes palindromes a fast disqualifier: a long line that starts and ends in the same row or box is usually a dead end, which is itself information.
How to start a board
- Pair the cells: first with last, second with second-last. Each pair is one digit in two places.
- Check whether any pair shares a row, column or box — if so, that digit is eliminated from both.
- The centre of an odd-length line is self-paired and gives nothing; ignore it until the end.
Common mistakes
- Reading the line as consecutive digits rather than mirrored ones.
- Forgetting that the mirrored cells may still conflict with the grid, which is the main source of eliminations.
- Assuming a palindrome cannot repeat a digit; repeats are the point.
Frequently asked questions
Does a palindrome have to be a straight line?
In most puzzle sets it is, but the rule only cares about order along the line, not geometry.
What does an even-length palindrome tell you?
Every digit appears an even number of times on the line — useful when one of those digits is nearly placed elsewhere.
Every board on this site is generated with a uniqueness check, so the puzzle in front of you has exactly one solution and every digit can be proved rather than guessed.
Play Palindrome Sudoku ↗