Sudokushort

Sudokushort is a compact data format and reference implementation for encoding Sudoku puzzles and their solutions as short strings. It aims to minimize data size for transmission and storage while preserving full puzzle content and metadata.

At its core, Sudokushort represents a 9x9 Sudoku grid by encoding the 81 cells into a compact string. Each cell value is encoded using a small symbol set (0 for empty, 1–9 for digits). A versioned header can precede the grid to indicate puzzle version, difficulty, and optional metadata such as author or time limit. The remaining grid data is encoded using a base-32/64-like alphabet to reduce length; common implementations offer both a fully compact form and a more verbose human-readable form with separators.

Reference implementations in multiple languages expose functions encode and decode, taking a grid or list of givens and returning a Sudokushort string, and vice versa. The format is lossless, with strict validation rules to ensure a valid 9x9 grid and consistency with Sudoku constraints.

Sudokushort emerged from an open-source puzzle community in the late 2010s as an efficient alternative to JSON or XML for sharing Sudoku challenges online. It is used in puzzle repositories, mobile apps, and competitive events to facilitate quick loading and compact storage.

Variants include human-readable encodings with punctuation for easy reading, and broadened schemas that also encode solution steps or solving hints. The format does not enforce Sudoku solving rules; it stores givens and solution state.

See also Sudoku, data encoding, puzzle formats.