HoDoKu online (no Java)

Bernhard Hobiger's HoDoKu (released up to version 2.2.0 in 2012) became the standard open-source sudoku solver, generator and trainer: its difficulty ratings, 90+ logical step finders and candidate coloring are referenced across sudoku books and forums. Because the original program was written for desktop Java Swing, running it today on macOS, Windows 11, Linux, iPhones, iPads or Android phones usually means installing a legacy Java Runtime Environment—or not running it at all on mobile.

Hodoku Revisited brings the complete HoDoKu 2.2.0 solving engine into the browser as pure TypeScript, with an offline-capable progressive web app and an interactive AI Coach.

Open HoDoKu in your browser Play today's Daily Puzzle

100% verified against HoDoKu 2.2.0

The solver engine was ported module by module—from Singles and Locked Candidates to Fish, Wings, Almost Locked Sets, AIC / Nice Loops, Forcing Chains & Nets, Kraken Fish and Templates. In automated golden tests against the original hodoku.jar across 587 puzzles and 34,672 solving steps, the port produces the exact same steps, in the same order, with the identical difficulty level and numerical score.

What is new in Hodoku Revisited

• AI Super Solver & Coach: Instead of spoiling a step all at once, click Coach me to walk through four Socratic stages (Where to look, The pattern, The logic, and Conclusion).
• “Why not?” Contradiction Prover: Select any empty cell on the board and click Why not D? for any candidate. The solver places that digit, propagates forced singles, prunes the trace to the shortest causal path, and draws the house-aligned chain that leads to a contradiction.
• Shareable Proof & Step Links: Share a direct URL to any puzzle, daily challenge, AI Coach walkthrough (?coach=1), or contradiction proof (?prove=r1c9.4).
• HoDoKu Modes & Formats: Supports Playing, Learning and Practicing modes, ColorKu balls, custom cell and candidate coloring, solution path stepping, extended booklet printing, and HoDoKu :0000:x:... library lines.

How to install on Mac, Windows, iOS and Android

You do not need an installer or Java:

1. Open /play/ in Chrome, Edge, Safari or Firefox.
2. On desktop (macOS, Windows, Linux, Chromebook), click the Install Hodoku Revisited icon in the address bar.
3. On iPhone or iPad (Safari), tap Share → Add to Home Screen. On Android (Chrome), tap Install app from the browser menu.

Once installed, a service worker caches the entire solver and puzzle bank on your device so you can generate, solve and analyze puzzles completely offline.