LZH

LZH is a family of lossless data compression algorithms and archive formats, best known for the LHA/LZH format used by the LHarc archiver. The compression combines a sliding-window dictionary (LZ77-style) with Huffman coding and, in many implementations, an optional LZSS-like encoding. Archives typically bundle many files and directories into a single file with an .lzh or .lha extension. The design emphasizes portability and simplicity on early personal computers.

Originating in Japan, the LHarc toolset was created by Haruhiko Okumura in the late 1980s and became widely used across DOS, Windows, Amiga, and Unix-like systems during the 1990s. Variants were developed independently, producing several compatible but divergent implementations.

Technical notes: LZH compresses data using a dictionary window and encodes matches as length-distance pairs and literals. The bitstream is produced by Huffman-coded blocks, allowing variable-length encoding. Some variants support file attributes, comments, and simple encryption. Archives can be segmented into multiple volumes, and archivers may offer options to balance compression ratio and speed.

Legacy and compatibility: LZH remains supported by some contemporary archivers (for example, 7-Zip and other multi-format tools), but it is less common than ZIP or 7z today. The format persists mainly in retro computing communities and certain older software distributions. The term LZH is often used interchangeably with LHA, though exact file contents may differ between tools.