The header can contain information about the version number where version numbers consist of two bytes. The file structure for 7z files begins with a “Signature Header”.

mcl-switch: 7-Zip uses local code page.

mcu-switch: if there are non-ASCII symbols then 7-Zip uses UTF-8 encoding.

If there are no required symbols, then the default mode uses UTF-8.

Per 's 7z history, beginning in 2008, 7z supported UTF-8 encoding for filenames.

Deflate, another LZ77 based compression algorithm.

BCJ2, converter for 32 bit x86 executables.

BCJ, converter for 32 bit x86 executables.

LZMA2, an improved version of the LZMA compression method.

LZMA is the default compression method for 7z files.

LZMA, an optimized version of the LZ77 compression algorithm.

The following are a list of compression methods, as stated by that are integrated with the 7z file format: More compression options may follow in time.

Support for solid compression, where multiple files of a similar type are compressed within a single stream.ħz files are compatible with several compression methods because of its open architecture.

Large file size support, up to 1600 terabytes.

High compression ratio (dependent on the compression method used).

An open architecture, which allows the support for a variety of compression methods.

According to, the official homepage for the 7-Zip file archiving program, the 7z file format has the following main features: There are other specification options from third-party sources including but not limited to py7zr, a 7z python library that also documents the file's key characteristics and structure. There is no formal format specification for 7z but the LZMA compression specification serves as an 'unofficial' specification with information on the file and byte structure. 7z was initially the default format for 7-Zip, developed by Igor Pavlov in 1999 that was used to compress groups of files. 7z is an archive file format that supports a variety of compression methods and encryption.

Converter 7z to zip