Media Kit
Press materials for Sudoku by Joseph
Quick Facts
| Developer | Joseph Keitgen — solo indie developer, Germany |
| First published | January 27, 2011 |
| Platforms | iOS (since 2011), Android (since March 2026) |
| Free trial | 7-day Premium trial included |
| App Store rating | 4.6 stars (10,700+ ratings across all countries) |
| Downloads | 800,000+ (iOS) |
| Languages | 46 |
| Website | sudokubyjoseph.app |
| Download link | get.sudokubyjoseph.app (auto-detects iOS / Android) |
| Press contact | support@keitgen.de |
The Story
Sudoku by Joseph is one of the longest-running Sudoku apps on the App Store. Joseph Keitgen first published it on January 27, 2011 — over 15 years ago. What started as a simple paid app called "Just Sudoku" has grown into a comprehensive puzzle platform with 12 variants, 200,000+ puzzles, and 800,000+ downloads.
The app has been built and maintained entirely by one person — no team, no venture capital. Apple featured it in their "Test Your Brain" editorial collection across 48 countries, and it was highlighted in MacStories' App Debuts (Club MacStories, January 2018).
In July 2021, severe flooding in western Germany damaged Joseph's home. The rebuild took years, which is the honest reason the app went without a major update for so long. The March 2026 release — the biggest in 15 years — marks a full comeback: a ground-up rebuild with 10 new puzzle variants, a complete redesign, and an Android launch.
What's in the App
12 Puzzle Variants
One of the app's strongest differentiators is the breadth of Sudoku variants — many of which are extremely hard to find in any other single app.
Difficulty That Means Something
Unlike most Sudoku apps that simply remove more numbers to increase difficulty, Sudoku by Joseph uses actual solving techniques to define each level — from Casual (quick fix while waiting in line) through Easy, Medium, Hard, and Expert, all the way to Diabolical (for players who know what X-Wing, Swordfish, and XY-Wing techniques are). Every puzzle has exactly one solution. No guessing required.
Visual Customization
13 color themes (all free, light and dark mode), customizable fonts, and the option to play with emojis instead of numbers — 14 symbol styles in total. Daily Challenge with streaks rounds out the experience.
Gameplay Options
Extensive options to customize the gameplay experience: auto pencil marking, multiple input modes, and unlimited hints for Premium subscribers. The app works completely offline and respects player privacy — no data collection, no tracking.
Free vs. Premium
The app is free to download and includes a 7-day Premium trial.
| Feature | Free | Premium |
|---|---|---|
| Puzzle Variants | ||
| Classic, Jigsaw, Killer | ✓ | ✓ |
| Samurai, Kazaguruma, Flower, Sohei, Butterfly, Tripledoku, Gattai-3, Cross, 16x16 | — | ✓ |
| Features | ||
| Daily Challenge & Streaks | ✓ | ✓ |
| 6 Difficulty Levels | ✓ | ✓ |
| 13 Color Themes | ✓ | ✓ |
| Customizable Fonts | ✓ | ✓ |
| Play with Emojis (14 symbol styles) | — | ✓ |
| Auto Pencil Marking | — | ✓ |
| Unlimited Hints | — | ✓ |
| Ad-free | — | ✓ |
Screenshots
iPhone screenshots — tap to enlarge. Additional screenshots including iPad, with and without device frames, are included in the downloadable press kit below.
Tap to enlarge
Download Press Kit
All screenshots (iPhone and iPad, with and without device frames) and the app icon in various sizes.
ZIP, ~30 MB — Screenshots (iPhone + iPad), App Icon
Need assets in a different format or resolution? Just get in touch.
Story Angles
A few directions that might resonate, depending on your audience.
One of the App Store's longest-running puzzle apps gets its biggest update ever. What does indie longevity look like when most apps disappear within a year?
Most people know classic Sudoku. But Samurai (five overlapping grids), Kazaguruma (a pinwheel of four), and Flower puzzles take it to another level entirely. The more you play standard Sudoku, the more it becomes pattern recognition — variant puzzles force your brain into genuinely new territory. An exploration of variants most players have never seen.
In a mobile world designed to keep you scrolling, Sudoku by Joseph does the opposite. No coins, no lives, no wait timers, no video ads interrupting your flow. The app is built for calm, focused engagement — what some players describe as their daily form of meditation. A conscious alternative to the dopamine treadmill of social media.
Research supports this: structured puzzle-solving promotes mindfulness and cognitive closure — the opposite of the anxiety loop that passive scrolling creates.
A 2025 Lancet cohort study found that regular puzzle solvers maintained executive function equivalent to seven years younger. A UCLA study showed daily Sudoku improved working memory by 18% over six months. And research from UAlbany specifically found that gradually increasing difficulty — exactly what the technique-based difficulty system in this app does — produces greater cognitive benefits than staying at one level. For seniors especially, it's a low-barrier way to stay engaged with logical thinking.
Sources: The Lancet "Puzzles for Longevity" (2025), UCLA Working Memory Study (2024), University at Albany (2025)
Most Sudoku apps increase difficulty by simply removing numbers from the grid. Sudoku by Joseph defines difficulty by the actual solving techniques required — naked pairs, X-Wing, Swordfish. It's the gold standard in serious puzzle communities, and it's what separates a challenging puzzle from an unfair one.
No lives system, no coin economy, no wait timers, no gacha mechanics. In a category dominated by manipulative free-to-play models, one app bets entirely on the quality of its puzzles. A story about what it means to respect your players in 2026.
Link to the App
This universal link auto-detects whether the visitor is on iPhone or Android and sends them to the right store.
Get in Touch
For press inquiries, review copies, promo codes for your audience, or interviews — reach out at support@keitgen.de. I read everything and respond personally.