Everything else is standard Sudoku. The lines turn distant cells into pairs that must hold the same digit, which lets information jump across the board.
Palindrome Sudoku rules in 30 seconds
- 1Every row, column and 3×3 box contains 1–9 exactly once.
- 2Each grey line reads the same forwards and backwards.
- 3First cell equals last cell, second equals second-last, and so on.
- 4On an odd-length line, the centre cell has no partner.
See it on a board
Watch: how to play Palindrome Sudoku
Still not sure? Some puzzles click faster when you see them solved. This 17-minute video from Steven Scott shows Palindrome Sudoku in action.
Fold the line in half
The easiest way to read a palindrome is to imagine folding the line at its middle. Cells that land on each other must contain the same digit. The shape doesn't matter: lines can bend and turn, and what counts is the order of cells along the line, not how far apart they are on the board.
Odd and even lines
An odd-length line, like 4 → 9 → 2 → 9 → 4, has one centre cell that mirrors itself and can be anything. An even-length line, like 3 → 7 → 7 → 3, pairs every cell with a partner. Note that two mirrored cells next to each other must be in different rows or columns, or they couldn't hold the same digit.
Worked example: intersecting candidates
- 1Two cells are mirrored on a palindrome, so they hold the same digit.
- 2From its row and column, the first can only be 2, 5 or 7.
- 3From its own row and column, the second can only be 5, 7 or 9.
- 4The shared digit must be in both lists, so it's 5 or 7, and both cells get that shorter list.
Palindrome Sudoku tips and strategies
Copy every placement across
The moment one cell on a line is known, its mirror partner is known too.
Treat pairs as one cell
A mirrored pair must avoid every digit that either cell's row, column or box already has.
Watch the givens
A given digit on a palindrome instantly solves its partner.
Count carefully on bent lines
Match cells by their position along the line, not by where they sit on the board.
Common mistakes to avoid
- Matching cells by board position instead of line order.
- Forgetting that the centre of an odd line pairs with itself.
- Solving each side of a line separately instead of combining their restrictions.
Play Palindrome Sudoku in 10+ Number Puzzles
- Palindrome lines stay drawn under the digits as you highlight rows, columns and boxes.
- Auto Notes respects both the Sudoku rules and the mirrored pairs.
- You have 3 lives. A wrong digit costs one.
- Five difficulty levels, each a ladder of stages from Easy to Genius.
- Go online for free: ranked 1v1 duels, rooms where you race, co-op or play in teams, and tournaments.
- 27 more puzzle types in the same app, and online play never costs coins.
Palindrome Sudoku FAQ
What is a palindrome in Sudoku?
A line of cells whose digits read the same in both directions, so the first matches the last, the second matches the second-last, and so on.
Can palindrome lines bend?
Yes. Follow the line cell by cell. Its shape on the board doesn't change the rule.
Does the middle cell of a palindrome have to match anything?
On an odd-length line the centre cell mirrors itself, so it has no partner to match.
