--- title: "Why Medium Sudoku Suddenly Feels Harder | Sudoku Flow" description: "In our app, Medium Sudoku needs a move Easy never does: a digit with only one place left. What changes, when it happens on a real puzzle, and how to find it." url: https://sudokuflow.com/guides/why-is-medium-sudoku-harder/ language: en last_modified: 2026-11-06 --- [Sudoku guides](https://sudokuflow.com/guides/) # Why Medium Sudoku Suddenly Feels Harder In our app, Medium Sudoku needs a move Easy never does: a digit with only one place left. What changes, when it happens on a real puzzle, and how to find it. Updated 2026-11-06 ## Quick answer In our app, Medium asks for a new kind of move. On Easy, there is always a square with only one digit left. On Medium, those run out, and the next move is a digit with only one place left in a row, column or box: a hidden single. Every Medium puzzle in our app needs that move and no Easy puzzle does, and Medium starts with 36 givens instead of 51. - Easy can be finished by looking at one square at a time. - Medium needs hidden singles: ask where a digit can go, not what a square can hold. - For 100.0% of our Medium puzzles, the hidden single is the hardest step. - Medium starts with 36 givens, Easy with 51. - Our players' median time goes from about 3 minutes on Easy to about 7 on Medium. ## What changes from Easy to Medium In our app, a puzzle's level is set by the hardest step it needs. Easy puzzles never need more than a square with one digit left. Medium puzzles need the hidden single: for 100.0% of them it is the hardest step. They also start with fewer digits, 36 instead of 51, so there is more to work out. You feel it on the clock. The median Easy game our players win without a hint takes about 3 minutes; on Medium, about 7. [What each Sudoku difficulty level asks of you →](https://sudokuflow.com/data/sudoku-difficulty-levels/) ## The moment it happens This is the first Medium puzzle from our printable Sudoku, with 36 digits given. Filling in every square that has only one digit left adds 14 digits, shown in blue, and then there are none left. The marked square could still hold 2 digits, so looking at it alone does not help. Looking at one digit does: ```text . 4 5 | . 7 . | 1 . 2 . 3 . | 1 2 . | 9 . 5 1 8 2 | . . . | 7 . 6 ------+-------+------ . 9 . | . . . | 6 2 3 . . . | . . 2 | 4 1 8 8 2 1 | 3 6 4 | 5 9 7 ------+-------+------ 3 5 9 | 2 4 7 | 8 6 1 . . . | . 3 . | 2 5 . 2 1 . | 5 8 . | 3 7 . ``` *Medium, sheet 1, puzzle 1: no square has only one digit left, and the marked square is the next move.* **Row 1, column 1: 9**. 9 has only one place left in its box. ## How to find a hidden single - Pick a digit, for example 1. - Look at one box. Every row and column that already holds that digit rules out its squares in the box. - If only one empty square is left, the digit goes there. - Do the same with rows and columns, then move on to the next digit. - Each digit you place can open new moves, so go round the digits again. [Hidden Single →](https://sudokuflow.com/lessons/hiddenSingle/) [Medium Sudoku →](https://sudokuflow.com/play/medium/) ## Tips for Medium - Scan by digit, not by square: that is the switch Medium asks for. - Start with a digit that is already placed many times: it has the fewest copies left to place. - You do not need notes yet. Every Medium puzzle in our app can be finished with these two kinds of single. - When Medium feels easy, Hard adds moves that rule out candidates, and that is where notes start to help. [Stuck on a Hard or Expert Sudoku? The Technique You Need Next →](https://sudokuflow.com/guides/stuck-on-hard-sudoku/) ## Practice Every Find the Mistake puzzle on this site has exactly one wrong digit, and you can play each board right on its page. [Play the puzzles →](https://sudokuflow.com/puzzles/) ## Sudoku guides - [How to Find a Mistake in Sudoku](https://sudokuflow.com/guides/find-a-mistake/) - [7 Common Sudoku Mistakes and How to Avoid Them](https://sudokuflow.com/guides/common-mistakes/) - [Why Won't My Sudoku Solve? A Checklist](https://sudokuflow.com/guides/sudoku-wont-solve/) - [Naked Single vs Hidden Single](https://sudokuflow.com/guides/naked-single-vs-hidden-single/) - [Pointing Pair vs Box/Line Reduction](https://sudokuflow.com/guides/pointing-pair-vs-box-line-reduction/) - [X-Wing vs Swordfish](https://sudokuflow.com/guides/x-wing-vs-swordfish/) - [How to Start a Sudoku: The First Five Minutes](https://sudokuflow.com/guides/how-to-start-sudoku/) - [Stuck on a Hard or Expert Sudoku? The Technique You Need Next](https://sudokuflow.com/guides/stuck-on-hard-sudoku/) - [Sudoku Tips That Actually Work (and Is There a Formula?)](https://sudokuflow.com/guides/sudoku-tips/) - [How to Teach a Child Sudoku: 4×4, Then 6×6, Then 9×9](https://sudokuflow.com/guides/teach-kids-sudoku/) - [Can Every Sudoku Be Solved Without Guessing?](https://sudokuflow.com/guides/solve-without-guessing/) - [Which Sudoku Techniques Do You Actually Need? 60,000 Puzzles Counted](https://sudokuflow.com/guides/sudoku-techniques-you-need/) - [How to Solve Sudoku Faster](https://sudokuflow.com/guides/solve-sudoku-faster/) - [Do the Diagonals Count in Sudoku? Diagonal Sudoku (Sudoku X) Rules](https://sudokuflow.com/guides/diagonal-sudoku-rules/) - [How to Solve Killer Sudoku: Where to Start](https://sudokuflow.com/guides/how-to-solve-killer-sudoku/) - [Jigsaw Sudoku Rules and How to Start](https://sudokuflow.com/guides/jigsaw-sudoku-rules/) - [6×6 Sudoku: Rules and Tips for Beginners](https://sudokuflow.com/guides/6x6-sudoku-rules/) - [How to Solve Samurai Sudoku: Where to Start](https://sudokuflow.com/guides/how-to-solve-samurai-sudoku/) - [Is Sudoku Math? Logic, Not Arithmetic](https://sudokuflow.com/guides/is-sudoku-math/) - [Can a Sudoku Have Two Solutions?](https://sudokuflow.com/guides/can-sudoku-have-two-solutions/) - [How Long Does a Sudoku Take? Times by Level](https://sudokuflow.com/guides/how-long-does-sudoku-take/) - [How to Make a Sudoku Puzzle, by Hand or by Program](https://sudokuflow.com/guides/how-to-make-a-sudoku/) - [16×16 Sudoku: Rules and How to Start](https://sudokuflow.com/guides/16x16-sudoku-rules/) - [Sudoku Notes: When and How to Use Pencil Marks](https://sudokuflow.com/guides/sudoku-notes-pencil-marks/) - [Sudoku for Seniors: Large Print Puzzles and How to Start](https://sudokuflow.com/guides/large-print-sudoku-for-seniors/) - [Wordoku: Sudoku with Letters Instead of Numbers](https://sudokuflow.com/guides/wordoku-letter-sudoku/) - [What each Sudoku difficulty level asks of you](https://sudokuflow.com/data/sudoku-difficulty-levels/) - [Sudoku facts](https://sudokuflow.com/guides/sudoku-facts/) - [Sudoku checker](https://sudokuflow.com/tools/sudoku-checker/) - [Sudoku for kids](https://sudokuflow.com/printables/kids/) - [Find the Mistake Sudoku](https://sudokuflow.com/find-the-mistake/) ![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.