7Z file type: 7-Zip archive format

What is a .7z file

7Z extension designates a popular archiving format, created for 7-Zip, a modern file archiver application written by Igor Pavlov and released as freeware and Open Source software. 7-Zip (often incorrectly shortened in 7zip) was originally developed for Microsoft Windows platforms, and ported by p7zip (POSIX-7Zip) project team on Unix platforms.
Spanned multi-volume 7z archives are designated by .001 extension, incrementing file extension numerator for each successive volume of the set - spanned 7z files are split byte-wise, this raw splitting mechanism being compatible with Unix / Linux "split" command and Windows utilities like HJSplit.

PeaZip support for .7z file type

PeaZip supports creation and extraction of 7z files: create, open, browse, and extract 7Z archives, convert any supported archive to 7z format and vice-versa.

Maximum number of files in a 7z archive

As maximum number of input files per archive, 7z format allows to store up to 2^32 files (unsigned dword, 4 giga files), exceeding current practical limits.

Maximum size of each file in a 7z archive

7z format can accept input files up to 2^64 bytes in size (16 exabytes, each), far exceeding current needs and limits of most current filesystem implementations.

Maximum total size of 7z archive

7z file can theoretical be up to 2^64 bytes in size (16 exabytes of total size of the archive), far exceeding current needs and capabilities of filesystems as currently implemented.
In example

• FAT32 filesystem allows files up to 2^32 bytes (4GB in size)
• NTFS filesystem allows max file size of 2^64 bytes (16 EB) but implementations allows lower maximum sizes, 16 TB in Windows 7, 256 TB in Windows 8, 8 PB in Windows 10
• exFAT filesystem theoretically allows 2^64 bytes max file size (16 EB), but current implementation is limited to 128 PB

Features of .7z file format

7Z features very high compression ratio through powerful compression algorithms (LZMA, LZMA2, PPMd, BZip2, optionally optimized Deflate), at cost of more memory and CPU intensive compression process - that however can take benefit of parallel computing on modern multicore CPUs.
With Tino Reichardt's codecs for Brotli, Lizard, LZ4, LZ5, and Zstd algorithms, supported by PeaZip, 7z format features faster-than-zip compression / extraction.
On Linux and macOS additional codecs ofr .7z format is provided thorugh p7zip fork cielavenir/p7zip (LGPL, T. Yamada) which can be enabled setting 7z alias to "7zalt" in Options > Settings, Advanced tab.
On average test cases 7Z format improves compression ratio 30-70% better over classic ZIP format, and 6-7% better than RAR file format (WinRar's native format, proprietary); 7Z compression compares favourably also with new WinZip's ZIPX format in most cases.
7Z format also features native UTF-8 support for filenames, Rijndael / AES encryption, and volume spanning.

XZ file extension
XZ extension identify a pure compression format (compresses a single file, without offering option of archiving multiple input file into a single output .xz file), it is based on LZMA/LZMA2 algorithm family, featuring usual 7z-like compression ratio (similar or higher compared to RAR), recently often used on TAR files.

Read more about .7z extension: 7-Zip official domain, p7zip project POSIX port of 7-Zip for Unix and Unix-like operating systems, 7Z file format specifications, 7Z format Wikipedia entry, PPMd and LZMA / LZMA2 data compression algorithms.

Synopsis: 7Z file extension. What is 7Z file format, native 7-Zip archives type extension. What are XZ, LZMA, 7z files features and specifications, maximum size, max number of files limit. 7Z format superior compression ratio, compression speed, aes encryption and advanced format options. What is 7z archive format recommended for.

Topics: 7z file extension specs

PeaZip > FAQ > 7Z file extension, 7-Zip archive format