If you want to improve your Sudoku skills, Sudoku 401 will help you learn and play.

Sudoku 401 is a Sudoku game, a generator, a solver, and a teacher/tutor.

First, it is a serious Sudoku game.

- Puzzle generator for unlimited play. You will never see the same game twice.
- Clean and simple game board, so you can focus on the playing instead of being distracted by colors and/or shapes.
- Ability to enter the game manually, copy from newspaper, books, or other software.
- Tap on a clue to highlight potential locations for the number. Tap again to go back to normal viewing.
- Automatic or manual pencilmarks, which can be switched during the game play with one tap.
- Automatically saves the game when you leave, ability to continue when you come back.
- Option to use either symmetrically or non-symmetrical Sudoku boards.
- Option to show error.

Even more, it teaches you the logic and techniques of Sudoku, with its multi-step teaching system. All of the techniques are human logic, not computer brutal force.

- Difficulty level is defined by the techniques used, not by number of clues.
- Beginner: Full House, Hidden Single and Naked Single.
- Moderate: Hidden and Naked Pair, Locked Candidates.
- Challenging: Hidden and Naked Triple and Quad, X-Wing.
- Difficult: Swordfish, Jellyfish, XY-Wing and Finned X-Wing.
- Expert: Squirmbag, Finned Swordfish and Jellyfish (that also includes Fishy Cycle, Sashimi Fish and Turbot Fish), XYZ-Wing and WXYZ-Wing.
- Extreme: ALS-XZ (Almost locked set) and Finned Squirmbag.

Check out our screenshots to see how the teaching works.

What’s New

Version 3.0.8

Minor color changes.

Ratings and Reviews

4.0 out of 5
2 Ratings

2 Ratings

I think I will go on Vacation ,

Should be 5 stars but has a few minor nits

I was looking for a Sudoku app that could present very difficult puzzles, was easy to use, and worked well. This really fits the bill. I don't use the learning modes much so I can't comment on them. Oddly, the complaints I see appear to be related to the learning modes being too advanced or not adequately explained for that user. As for other comments: it is relatively easy to clear any specific square, just tap the square and touch the pencil mark or number.

Why only 4 stars. Here is the list of things I would change -
- need to require confirmation before pencil marking the entire board. It is too easy to accidentally tap that auto pencil mark button and it marks your entire board. Since the button is big this happens with some regularity and is very annoying.

- would be nice if it auto cleared pencil marks in a square, row, or column when the pencil marked number is completed. For example: I fill a 2 then I have to go clear the pencil marked 2's in the same row, column, and/or square. Yes, I know it has auto but that fills everything, it is just too much help. I just want to use what I marked but have a little automation.

- would be nice if we could clear the entire board and start over. Like pencil marks, this needs to have a confirmation so you don't accidentally kill off your game.

alanr50 ,

Needs some work

The game would have 5 stars with a few changes. Please consider the option of having the control grid in one place, off to the right would be great. I find it distracting to have it change location and cover the puzzle. Also the option of backing up or undoing an entry would be useful. It is easy to make a silly mistake, but there is no undo.
I am having a problem with the Difficult level. All I get are finned x-wings or variations of finned x-wing, no swordfish no jellyfish, and no xy-wing. This is a problem, it is getting predictable, there is a fault in the coding please fix it. As noted above the control box is a pain, my iPad has enough room to have it off to the side. I am changing my rating to three stars. Please fix the problems, this could be a great program.

JimWwww ,

Very educational; challenges you at exactly your level

This app can solve any sudoku, no matter how difficult.

But it doesn't just solve the puzzle – it TEACHES you how to solve it. Highly recommended!

Using techniques I learned in this game, I can solve most of the ones at the Difficult level, but the Expert and Brain Freeze levels are too much for me. The brain freeze is an in-app purchase, and it will definitely freeze whatever is inside your skull.

This is the most educational sudoku program available. It does things that no other sudoku can do. For me, the best feature is that it will give you an unlimited number of puzzles at precisely the level you are good at, or whatever level you wish. No more wasting time on puzzles that are much too easy. No more being frazzled by puzzles that are much too difficult.


John Huang
11.3 MB

Requires iOS 8.0 or later. Compatible with iPhone, iPad, and iPod touch.


English, Italian, Japanese, Korean, Portuguese, Spanish, Traditional Chinese

Age Rating
In-App Purchases
  1. Level 8: Brain Freeze $9.99


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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