AI Escargot Sudoku — Play It Online, With the Full Solution

Updated 15 October 2026

AI Escargot is a 23-clue sudoku that Finnish mathematician Arto Inkala published in 2006 and presented as the most difficult sudoku in the world. It is the puzzle most people find first when they search for the hardest sudoku ever made, and you can play it right here: the board below is the original grid, playable in your browser, printable, and solved step by step further down the page.

Clues

23

Published SE rating

SE 10.6

Suuudokuuu rater

8.5+, past every implemented technique

Play AI Escargot in the appPrint AI Escargot — PDF with the solution

Where AI Escargot comes from

The name pairs Inkala’s initials, AI, with escargot, the French word for snail. Inkala presented the grid as the hardest sudoku he knew of, the press repeated the claim in late 2006, and it became the reference “hardest sudoku” that solvers have studied more than almost any other grid.

It has since been overtaken. Rating tools in the Sudoku Explainer tradition put AI Escargot around SE 10.6, while later puzzles, including Inkala’s own 2012 Everest, sit at the top of the scale near 11.9. It remains the classic first attempt for anyone who wants to feel what a record puzzle is like.

Source: SudokuWiki, “AI Escargot”. The rating is the published figure the Infinity corpus carries, not a Suuudokuuu measurement; the full background on every record grid is on the hardest sudoku puzzles page.

The AI Escargot solution, step by step

Suuudokuuu’s source-available engine solves AI Escargot in 108 steps, reaching for the cheapest technique that still makes progress, exactly as it does when it rates a puzzle. 24 of those steps are forcing chains: the engine assumes a candidate, follows its consequences until something breaks, and removes the assumption. At 1 points even that runs dry — no technique the engine implements moves the grid — and the walkthrough says so, fills the cell with the fewest candidates from the verified solution, and carries on with logic from there. Every other step is a named deduction you can check by hand.

Along the way the walkthrough uses Full House, Naked Single, Hidden Single, Pointing Pair, Box Line Reduction, Naked Pair, Hidden Pair, Swordfish, Finned Swordfish, W-Wing, AIC and Nishio Forcing Chain.

The forcing chains are the heart of it. A Nishio forcing chain supposes one candidate is true and follows the singles it forces until a cell runs out of candidates, which proves the supposition false. To check any single step yourself, paste the grid into the step-by-step solver and replay it on a live board.