SudoCue - File Formats



As a courtesy to the people who want to write their own sudoku software, and those who like to learn more about the structure of sudoku files, this document describes the formats in the files created and recognized by SudoCue and SumoCue.

This documentation is up to date with version 1.4.1 of SudoCue. It was last updated on August 3, 2006.

We start with an overview of the file formats that this document explains.


A file containing a single sudoku puzzle. The format is based on the Sadman file format, with a few additions to include additional information.


A file containing a collection of sudoku puzzles. Each line contains a single puzzle.


A file containing your work in progress. Proprietary to SudoCue. Contains a candidate grid and identifies user digits as opposed to given digits.


A file containing details about the rating and required solving techniques for a collection of puzzles. Proprietary to SudoCue.


Extension and format used by Simple Sudoku. SudoCue can read an write the files produced by this popular program.

Sudoku Puzzle (.sdk)

The file contains 9 lines, reach representing a row in the puzzle. Empty cells are represented by a dot. Additional information is optionally present in separate lines, starting with a hash character, followed by a single letter that identifies the type of info:

  • A = Author
  • D = Description
  • C = Comment
  • B = Date published
  • S = Source (name of newspaper, book or website)
  • L = Level
  • U = Source URL

These additional lines are only recognized by SudoCue. Sadman sudoku also uses this format, but it does not recognize these entries.

An example:

#DA random puzzle created by SudoCue
#CJust start plugging in the numbers

Sudoku Puzzle Progress (.sdx)

This format contains a line for each row in the grid. A blank separates the cells. For unsolved cells, the candidates are listed without separating space. Solved cells are preceded by u when they are placed by the user, the givens have no prefix.

2 679 6789 1 46789 5 469 9 3
389 5 4 69 689 68 7 1 29
9 1 679 2 4679 3 4569 8 59
6 9 2 8 u1 7 3 59 4
3489 3479 3789 56 2456 46 u1 2579 2579
1 47 5 3 24 9 8 27 6
3459 2 39 7 3589 1 59 6 589
359 8 1 569 3569 6 2 4 579
7 369 369 4 35689 2 59 359 1

Sudoku Puzzle Collection (.sdm)

This is a very simple format. Each line contains a single puzzle. The empty cells are represented by a zero, but the program also accepts other placeholders, like a dot “.”. Line breaks in Windows or Unix style are recognized, but when my software writes these files, CrLb is always used. These files cannot be written by SudoCue. The program can only read them.


Simple Sudoku (.ss)

In a simple sudoku file, the data is stored in a human readable format.


There is an older format for Simple Sudoku files, which you may still encounter:


Collection file analysis (.scl)

There is a menu option File/Classify that can be used to mass-rate puzzle collections. When you select it, there will be a save dialog that allows you to name the .scl file to which the ratings will be written. For large collections with many extremely difficult puzzles, rating a collection will take a long time.
Here is an example of what you may see in a collection file:


The first line identifies the SudoCue rating file version. The second line is the path of the file that was rated. There is a line for each puzzle in the collection, it stars with the sequence number, followed by entries in (key=value) format, separated by a semicolon. The following table explains the meaning of each key:

RNumber of solving rounds
BBreath (not used in this version)
SRating score
IInitial singles
FHNumber of times the Full House technique is used.
D1Number of times the Last Digit technique is used.
M1Number of times the Mixed Single technique is used.
B1Number of times the Hidden Single in Box technique is used.
R1Number of times the Hidden Single in Row technique is used.
C1Number of times the Hidden Single in Column technique is used.
USNumber of times the Unlocked Single technique is used.
N1Number of times the Naked Single technique is used.
LPNumber of times the Locked Pair technique is used.
LTNumber of times the Locked Triple technique is used.
L1Number of times the Locked Candidates 1 technique is used.
L2Number of times the Locked Candidates 2 technique is used.
N2Number of times the Naked Pair technique is used.
N3Number of times the Naked Triple technique is used.
N4Number of times the Naked Quad technique is used.
H2Number of times the Hidden Pair technique is used.
H3Number of times the Hidden Triple technique is used.
H4Number of times the Hidden Quad technique is used.
X2Number of times the X-Wing technique is used.
X3Number of times the Swordfish technique is used.
X4Number of times the Jellyfish technique is used.
Y2Number of times the XY-Wing technique is used.
Y3Number of times the XYZ-Wing technique is used.
APNumber of times the Aligned Pair technique is used.
RPNumber of times the Remote Pair technique is used.
YCNumber of times the XY-Chain technique is used.
F2Number of times the Finned X-Wing technique is used.
F3Number of times the Finned Swordfish technique is used.
F4Number of times the Finned Jellyfish technique is used.
S2Number of times the Sashimi X-Wing technique is used.
S3Number of times the Sashimi Swordfish technique is used.
S4Number of times the Sashimi Jellyfish technique is used.
CTNumber of times the Color Trap technique is used.
CWNumber of times the Color Wrap technique is used.
MCNumber of times the Color Wing (MC) technique is used.
G1Number of times the BUG+1 technique is used.
MTNumber of times the Medusa Trap technique is used.
MWNumber of times the Medusa Wrap technique is used.
MBNumber of times the Medusa Bridge technique is used.
MXNumber of times the Medusa Complex technique is used.
U1Number of times the Unique Rectangle 1 technique is used.
U2Number of times the Unique Rectangle 2 technique is used.
U3Number of times the Unique Rectangle 3 technique is used.
U4Number of times the Unique Rectangle 4 technique is used.
ERNumber of times the Empty Rectangle technique is used.
ALNumber of times the Almost Locked Set technique is used.
NTNumber of times the Nishio technique is used.
TCNumber of times the Table Contradiction technique is used.
TVNumber of times the Table Verity/Veracity technique is used.
BFNumber of times Brute Force is used.
SRSurrender. When present, puzzle is unsolvable.
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