International Sudoku Day 2026 — 9 September
Every year on 9/9, Sudoku fans around the world mark International Sudoku Day — a nod to the nine rows, nine columns, nine boxes and nine digits of the classic grid. Here is the special 9/9 puzzle, why the date was picked, and a few ways to celebrate.
5 days until International Sudoku Day (Wednesday, September 9, 2026).
The 9/9 Sudoku —
This is the official Daily Sudoku puzzle for 9 September (Medium level).Get a head start now — it goes live with printable PDFs and the leaderboard on 9 September.
Leaderboard (Top 10)
Why is International Sudoku Day on September 9?
The date is a small joke every solver gets instantly: 9/9, for a 9×9 grid filled with the digits 1 to 9 — nine of everything. It was established by the World Puzzle Federation (WPF) — the international body that also runs the World Sudoku Championship — which declared 9 September International Sudoku Day in2013.
Since then, newspapers, puzzle apps, schools and clubs have used the day to run special grids and speed-solving events. On Daily Sudoku we keep it simple: the 9 September puzzle is the day's featured grid, and the whole archive going back to 2011 is open if one puzzle isn't enough.
A short history of Sudoku, in nine dates
- 1979 — Number Place is published in Dell magazines in the US, credited to architect Howard Garns.
- 1984 — Japanese publisher Nikoli picks up the puzzle and names it Sudoku, short for a phrase meaning "the digits must be single."
- 1997 — Retired judge Wayne Gould, visiting Tokyo, discovers Sudoku and spends years writing a computer program to generate puzzles.
- 12 November 2004 — The Times of London prints its first Sudoku, sparking the puzzle's newspaper boom.
- 2005 — Sudoku appears in newspapers across the US, Europe and beyond within a year of that first print run.
- 2006 — The first World Sudoku Championship is held in Lucca, Italy.
- 2011 — Daily Sudoku publishes its first puzzle, on 2011-04-28.
- 2013 — The World Puzzle Federation declares 9 September International Sudoku Day.
- 2026 — Solve this year's 9/9 puzzle above.
Read the full history of Sudoku for more.
Nine Sudoku facts for 9/9
- A completed Sudoku grid needs at least 17 clues to have a unique solution — fewer, and more than one valid grid fits.
- There are 6,670,903,752,021,072,936,960 possible completed 9×9 Sudoku grids — about 6.67 sextillion.
- The 9×9 grid is split into 9 boxes of 9 cells each, holding the digits 1 through 9 — nine 9s, which is why WPF picked 9/9.
- Despite the Japanese name, Sudoku's roots are American: it began as Number Place, a Dell magazine puzzle from 1979.
- Nikoli, the Japanese publisher that popularized it in 1984, named it Sūji wa dokushin ni kagiru — "the digits must be single" — shortened to Sudoku.
- The Times of London ran its first Sudoku on 12 November 2004, and the puzzle was in newspapers worldwide within a year.
- The first World Sudoku Championship was held in Lucca, Italy, in 2006.
- Speed-solving records for a standard 9×9 grid are under 90 seconds at championship level.
- 9 September was declared International Sudoku Day by the World Puzzle Federation in 2013 — nine years after the puzzle's newspaper debut.
Ways to celebrate 9/9
- Solve all five levels. Try the 9 September puzzle from Very Easy toVery Hard and see how far you get.
- Print a stack for others. Ourprintable PDFs come with answer keys — handy for a classroom, office or family table. There arekids' grids andlarge-print grids too.
- Learn one new technique. PickX-Wing orNaked Pairs from thetechniques guide and use it today.
- Try a variant. Killer Sudokuand Jigsaw Sudoku use the same digits with a twist.
- Revisit a date that matters to you. Thearchive has a puzzle for every day since April 2011 — a birthday, an anniversary, or last year's 9/9.
International Sudoku Day in the classroom
9/9 is an easy hook for a classroom brain-break: hand out grids, race the clock, or let kids check their own work. Ourprintable Sudoku for kids uses smaller 4×4 and 6×6 grids for beginners, every PDF has an optional answer key so students can self-check, and theSudoku for kids guide has tips for introducing the rules to a new solver.
Every past International Sudoku Day puzzle
Solve any 9 September grid from the archive, all the way back to our first year online.
- 2025 —
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- 2022 —
- 2021 —
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- 2011 —
Frequently asked questions
When is International Sudoku Day?
International Sudoku Day is on 9 September every year. The date was chosen because 9/9 echoes the 9×9 grid and the digits 1–9 used in a standard Sudoku.
Who created International Sudoku Day?
The World Puzzle Federation (WPF), the body behind the World Sudoku Championship, declared 9 September International Sudoku Day in 2013.
How do I celebrate International Sudoku Day?
Solve the 9/9 puzzle on this page, try all five difficulty levels, print a few grids for friends or a classroom, or learn a new solving technique such as X-Wing. Any day you solve a Sudoku counts.
Is the 9/9 puzzle free?
Yes. Like every puzzle on Daily Sudoku, it is free to play online and to print, with no signup.