--- title: "Evil Sudoku (Extreme): Play Free Online, No Ads | Sudoku Flow" description: "Play Extreme Sudoku free in your browser, with notes, undo and hints and no ads. Every puzzle has one answer and is graded by the technique it needs." url: https://sudokuflow.com/play/extreme/ language: en --- # Extreme Sudoku Other sites call puzzles this hard Evil or Diabolical Sudoku. Free Extreme Sudoku puzzles to play right here, with no ads and no sign-up. When you finish one, New puzzle gives you the next; your progress stays on this device. ## Extreme · #1 Daily Sudoku grid: ```text . 5 . | . 3 . | . . 4 . 3 . | 8 . 7 | . 1 . . . 4 | . . . | . . 3 ------+-------+------ . . . | . . . | 6 . . 3 . 7 | . 5 1 | . 8 . 1 . . | . 2 8 | . . . ------+-------+------ 9 . 8 | . . . | . . 2 . . . | 9 . . | 4 . . . . . | 7 . 2 | 1 . . ```
What does this puzzle need?
## What Extreme puzzles ask of you We re-solved all 9,376 Extreme puzzles in the app with its hint engine, always taking the easiest step that works. This is the hardest step each one needed: 1. [ALS-XZ](https://sudokuflow.com/lessons/alsXZ/) 86.3% 2. [Unique Rectangle](https://sudokuflow.com/lessons/uniqueRectangle/) 12.1% 3. [Finned X-Wing](https://sudokuflow.com/lessons/finnedXWing/) 1.2% 4. [Finned Swordfish](https://sudokuflow.com/lessons/finnedSwordfish/) 0.4% 5. [ALS-XY-Wing](https://sudokuflow.com/lessons/alsXYWing/) under 0.1% [What each Sudoku difficulty level asks of you →](https://sudokuflow.com/data/sudoku-difficulty-levels/) ## How to solve Extreme Sudoku What makes a puzzle Extreme is the hardest step it needs. Most often that step is ALS-XZ (86%) or Unique Rectangle (12%). Extreme puzzles need the deepest patterns in our app. Most are decided by ALS-XZ, which links two almost locked sets through a number they share, and the rest mostly by a Unique Rectangle, which uses the fact that the puzzle has only one solution. Expect to spend a while on one step. [Learn ALS-XZ step by step →](https://sudokuflow.com/lessons/alsXZ/) ## Extreme Sudoku: questions and answers ### How many numbers do Extreme puzzles start with? Extreme puzzles here start with 26 to 28 of the 81 squares filled in, most of them with 26. ### Do Extreme puzzles need guessing? No. Every puzzle has exactly one solution, and the hint engine of our app solves each one with logic alone, one technique at a time. ### Can I get a hint while I play? Yes. Hint names the technique the next step needs and shows it on your board one step at a time, with the same hint engine our app uses. ### What comes after Extreme? Extreme is the hardest of the six levels. ## All six levels - [Easy Sudoku](https://sudokuflow.com/play/easy/) Nearly Complete (95%) - [Medium Sudoku](https://sudokuflow.com/play/medium/) Hidden Single (100%) - [Hard Sudoku](https://sudokuflow.com/play/hard/) Pointing Pair (60%), Naked Pair (18%), Box/Line Reduction (13%), or Hidden Pair (6%) - [Expert Sudoku](https://sudokuflow.com/play/expert/) Skyscraper (55%), Y-Wing (30%), or Empty Rectangle (6%) - [Master Sudoku](https://sudokuflow.com/play/master/) XY-Chain (59%), W-Wing (28%), X-Chain (6%), or XYZ-Wing (5%) - **Extreme Sudoku** ALS-XZ (86%) or Unique Rectangle (12%) ## More Sudoku to play - [Print Extreme Sudoku](https://sudokuflow.com/printables/sudoku/extreme/) - [Daily Sudoku: four new puzzles every day](https://sudokuflow.com/daily/) - [Sudoku checker](https://sudokuflow.com/tools/sudoku-checker/) - [Sudoku for kids](https://sudokuflow.com/printables/kids/) - [The world's hardest Sudoku](https://sudokuflow.com/data/hardest-sudoku/) ![Sudoku app icon](https://sudokuflow.com/assets/app-icon.png) ## Want more boards like this? We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number. [App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_web&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dweb%26utm_campaign%3Dsite) Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.