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Why Sudoku Difficulty Varies Between Apps

Learn how DailySudoku sets difficulty and why puzzles at the same level can feel different, with measured results and two example boards.

Written by
DailySudoku editorial team (Object)
Published
2026-09-22
Updated
2026-09-22

Two ways to rate difficulty

Sudoku apps generally rate difficulty in one of two ways.

  • By the number of givens: fewer numbers filled in at the start, or givens, are treated as harder. This is simple to set and anyone can count them.
  • By the techniques required: the rating depends on the methods you need to finish the puzzle, such as a Naked Single, a Naked Pair or more complex relationships.

These approaches can rate the same puzzle differently. A puzzle with few givens may need only easy techniques, while one with many givens may need complex ones. That is why one app's “Hard” can feel like another app's “Medium.”

Difficulty in DailySudoku

DailySudoku sets difficulty by the number of givens. When generating a puzzle, it starts with a completed grid and removes givens one by one, keeping each removal only if uniqueness is preserved: exactly one solution remains. It stops when it reaches the target count for that difficulty.

  • Easy: 40 givens at the start
  • Medium: 32
  • Hard: 28
  • Expert: 24
  • Master: a target of 22; if the target cannot be reached, it uses the puzzle it found with the fewest givens

Today’s puzzle (the daily puzzle) is always Medium. Higher difficulties also give you more base points on completion, from 1,000 for Easy to 7,000 for Master.

Why puzzles at the same difficulty feel different — measured results

Having the same number of givens does not mean puzzles need the same techniques to finish. The editorial team generated 200 puzzles at each difficulty with this app's generator, sudoku-core 1.0.0, and counted how many could be completed using only Naked Singles and Hidden Singles, the two methods in the rules article (2026-09-22).

  • Easy: all 200 out of 200 puzzles could be completed with just the two methods.
  • Medium: 180 out of 200
  • Hard: 147 out of 200
  • Expert: 101 out of 200
  • Master: 90 out of 200

Of the 200 Master puzzles, 93 actually had 22 givens, 103 had 23, and 4 had 24. These figures come from one generated sample, and results can vary between puzzles.

As difficulty rises, fewer puzzles can be finished with just the two methods. Even so, about three quarters of Hard puzzles need only those methods, while some Medium puzzles leave you stuck with them. This explains why one puzzle at a given difficulty flows easily while another stops you.

Example — two puzzles with exactly 28 givens

Both puzzles below are Hard, with 28 givens each.

c1c2c3c4c5c6c7c8c9
r1r2r3r4r5r6r7r8r9
1
9
7
3
8
6
3
1
8
7
5
6
3
5
7
7
2
9
1
1
6
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7
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Hard puzzle ①. 28 givens. You can finish it using only the two methods.
c1c2c3c4c5c6c7c8c9
r1r2r3r4r5r6r7r8r9
3
4
7
6
7
9
4
8
1
7
3
1
9
8
2
6
9
2
6
4
4
8
2
5
2
3
7
1
Hard puzzle ②. 28 givens. The two methods fill 31 cells, then leave you stuck with 22 cells remaining.

In puzzle ①, alternating between the two methods from the rules article fills all 53 empty cells. In puzzle ②, the same methods fill 31 cells, then leave you with 22 cells and no further answer you can determine. From there, you need to write candidates and look for relationships such as Naked Pairs.

Despite having the same number of givens, these puzzles feel very different. The difficulty label tells you where you start, but not which techniques the puzzle will require.

Choosing a difficulty

  • Easy: suited to learning the rules. All 200 sampled puzzles could be solved with the two methods alone.
  • Medium and Hard: most puzzles can be solved with the two methods, but some will leave you stuck. If that happens, follow Stuck on Sudoku? A 7-Step Checklist.
  • Expert and Master: in the sample, nearly half of Expert puzzles and more than half of Master puzzles could not be completed with just the two methods. You will need candidates and Naked Pairs, or more complex techniques, so learn candidate notes before trying these levels.

Common mistakes

  • You judge a puzzle by its difficulty label alone. Even with the same label, the techniques required vary from puzzle to puzzle.
  • You directly compare difficulty labels across apps. If apps rate difficulty differently, the same name does not mean the same challenge.
  • You blame only your ability when you get stuck. As the measurements show, even at one difficulty, some puzzles require more complex techniques.

Practice puzzle

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r1r2r3r4r5r6r7r8r9
5
2
7
6
9
3
7
4
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8
7
5
8
7
3
3
5
2
4
8
2
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6
1
2
9
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1
3
Practice board. Count the givens at the start to identify the difficulty.

What difficulty is this puzzle in DailySudoku? Count the numbers filled in at the start and compare the total with the given counts above.

Show answer

Medium. There are 32 numbers filled in at the start, and 32 is the given count for Medium.

Prerequisites

Introductory

Sudoku Rules: A 3-Minute Guide

Learn the three rules for rows, columns and 3×3 boxes, and two ways to find your first number on an example board.