Medium Between Lines Sudoku

Digits on each line must fall between the values at its endpoints. Every line adds a range constraint to the standard rules.

Easy Medium Hard Expert

Between Lines Sudoku at medium difficulty. Cells shared by two lines must satisfy both ranges at once — these intersections are the key to unlocking medium puzzles.

6
9
5
6
7
4
3
3
9
6
2
8
1
2
3
1
6
9
8
3
5
1
3
9
2
8
3
9
4
8
4
6
Mistakes
0/3
Score
-
Time
00:00
Try Hard Between Lines Sudoku →
Progress0%

What is Between Lines Sudoku?

Difficulty
★★★☆☆
3/5
Constraint Type
Line Constraints
Typical Givens
20–28
Avg. Solve (Medium)
18 min

Solving Techniques for Medium Level

Technique Description Level
Endpoint Gap Analysis The gap between endpoint values must be large enough to accommodate all middle cells. If endpoints are 2 and 8, middle cells must come from {3,4,5,6,7}. Beginner
Endpoint Ordering The endpoint values have no fixed order — the constraint is that all middle cells are strictly between the minimum and maximum endpoint. Beginner
Tight Endpoint Constraint If endpoints would be consecutive (e.g., 3 and 4), no middle cell could satisfy the strict inequalities — use this to force endpoints apart. Intermediate

Master these, then take on Hard Between Lines Sudoku to learn Advanced techniques.

Techniques to Master at Medium

  • Hidden Singles technique — With 1 and 9 barred from every line interior, they crowd into the few off-line cells of crossing rows and boxes — between grids mass-produce hidden singles on the extremes.
  • Obvious Pairs technique — Endpoint circles of a short line are often forced apart into {1,2}-low versus {8,9}-high options — the two circles behave as a long-distance pair across their shared units.

Average Solve Time by Difficulty

Easy
8 min
Medium
18 min
Hard
36 min
Expert
64 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Between Lines Sudoku →

Related Variants

Palindrome Sudoku

Another variant where a line links far-apart cells — mirrored digits there, a shared value range here.

German Whispers

Inverts the comfort zone: between lines squeeze digits into a narrow range while whispers force them far apart.

Thermo Sudoku

Adds full ordering to the range logic you use on between lines — every step along a thermometer must increase.

Frequently Asked Questions — Medium Between Lines Sudoku

What techniques help with medium Between Lines Sudoku?
At medium difficulty, combine endpoint-range reasoning with standard naked pairs and hidden singles. When you determine one endpoint's value, the range of valid middle digits becomes fixed. Cross-reference those valid digits with row, column, and box constraints to eliminate candidates from middle cells.
How do overlapping between lines interact?
When a cell is the middle of two different between lines, it must satisfy both lines' range constraints simultaneously. This intersection is extremely constraining — the cell must be strictly inside both ranges at once. Look for cells that appear on multiple lines; they often reveal the tightest constraints.
What is endpoint-value reasoning in Between Lines Sudoku?
Endpoint-value reasoning means determining the possible values for the circle cells by working backward from the middle cells. If the middle cells can only contain certain digits, the endpoints must be below the minimum and above the maximum of those digits. Narrowing the endpoint range is often the key to unlocking medium puzzles.
Should I use pencil marks for medium Between Lines Sudoku?
Yes. Mark the candidate digits for each cell using standard constraints, then further restrict each middle cell to only those candidates that fall strictly between the currently possible endpoint values. This range-aware initialization often halves the candidate count in middle cells immediately.
How long does a medium Between Lines Sudoku take?
Most players finish a medium Between Lines Sudoku in 15–28 minutes. Players who use endpoint-range reasoning from the start consistently solve faster than those who discover the between constraint only when stuck.

More questions? See the full Between Lines Sudoku guide.