Time00:00
Mistakes0/3
Hints3
1Tap a cell to select, then tap a number to fill it in
2Each row, column, and 3×3 box must contain 1-9 with no repeats
33 mistakes and the game is over
4Use toolbar to undo, erase, or get hints
1-9 1-9: Place number in selected cell
⌫ Backspace/Delete: Erase selected cell
Ctrl+Z Ctrl+Z: Undo last move
←↑→↓ Arrow keys: Navigate between cells
What is Daily Diagonal Sudoku?
Daily Diagonal Sudoku adds two extra constraints to the classic 9×9 grid: both main diagonals (from top-left to bottom-right and from top-right to bottom-left) must also contain the digits 1 through 9 exactly once. Standard row, column, and 3×3 box rules still apply.
This variant only supports Easy, Medium, and Hard difficulty — the weekly expert day is capped at Hard. The daily puzzle is the same for every player worldwide, refreshed at midnight UTC.
Why Play Daily Diagonal Sudoku?
Extra Challenge Layer
Two diagonal constraints mean fewer candidates per cell — perfect for solvers who find classic Sudoku too easy.
Fresh Puzzle Daily
A brand-new diagonal Sudoku every day at midnight UTC. Same puzzle for all players worldwide.
Track Your Streak
Build a daily habit with streak tracking. How many consecutive days can you solve?
Full Archive Access
Play any past date going back to day one. Master every difficulty at your own pace.
Play Instantly
No sign-up, no ads, no downloads. Open and play right in your browser.
Works Everywhere
Fully responsive design — play comfortably on desktop, tablet, or phone.
Diagonal Sudoku Solving Tips
✓Check Both Diagonals First — Before placing a number, verify it doesn't already appear on either diagonal that passes through that cell.
✓Diagonal Intersections — The center cell (5,5) lies on both diagonals. Use this to your advantage — it's the most constrained cell on the board.
✓Diagonal Scanning — Scan diagonals the same way you scan rows and columns. A missing digit on a diagonal often reveals placements quickly.
✓Corner Cells — Corner cells each lie on one diagonal. When a diagonal is nearly complete, the remaining corners are easy to fill.
✓Cross-Reference — Use diagonal constraints together with row/column constraints. A number excluded from a diagonal position narrows candidates in that row or column.
✓Use Pencil Marks — Mark candidates considering all five constraint groups (row, column, box, main diagonal, anti-diagonal).
✓Start at the Center — The center cell is part of four constraint groups (row, column, both diagonals). Solving it early reduces possibilities across the entire grid.