Microsoft KWAJ installation compression

File Format
Name	Microsoft KWAJ installation compression
Ontology	Electronic File Formats Compression Microsoft KWAJ installation compression
Extension(s)	.??_, .??$
PRONOM	fmt/469
Wikidata ID	Q105850885

Microsoft KWAJ installation compression refers to a compressed file format used for software installation by Microsoft and their installer tools. "KWAJ" refers to the signature bytes at the beginning of a compressed file.

KWAJ is a relative of some similar formats, most importantly the one known as "SZDD". For the other formats, see MS-DOS installation compression and Microsoft SZ installation compression.

KWAJ is more sophisticated than SZDD, though the relationship between them is not clear.

Format details

There is a 16-bit field at offset 8 that specifies the compression or encoding method.

Compression code	Description
0	Uncompressed (rare)
1	XOR (rare)
2	Okumura's LZSS
3	LZ77 + Huffman
4	MSZIP (based on DEFLATE)

Identification

File begin with bytes 4b 57 41 4a 88 f0 27 d1.

Specifications

• libmspack: COMPRESS.EXE file formats

Software

• libmspack
• MSDN Library - April 1996 → MSDN15_1.iso → MSDNSMPL/PROD/EISPAK11/DECOMP.EXE - Decompression utility for DOS; supports compression methods 2, 3, 4

See also MS-DOS installation compression#Software.