Guide

7-Zip and 7z Format: The Complete Technical Guide

Q: Why does 7z achieve better compression than ZIP even at equivalent settings?

7z&#039;s superior compression comes from two main advantages. First, solid compression: 7z concatenates all files into a single stream before compressing, allowing the LZMA2 algorithm to find repeated patterns across file boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each file independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder instead of Huffman coding, which more precisely models symbol probabilities and approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% smaller than ZIP for software distributions.

Q: What is the difference between &quot;7z x&quot; and &quot;7z e&quot; commands?

&quot;7z x&quot; extracts with full paths — it recreates the directory structure from the archive in the output location, preserving the folder hierarchy. &quot;7z e&quot; extracts everything to the current directory without any folder structure — all files land flat in the destination, regardless of how they were organized in the archive. If two files in the archive have the same name in different directories, &quot;7z e&quot; will overwrite one with the other. Always use &quot;7z x&quot; when you want to preserve directory structure, and &quot;7z e&quot; only when you know the archive contains flat files or you intentionally want all files in one directory.

Q: Why does 7z achieve better compressão than ZIP even at equivalent settings?

7z&#039;s superior compressão comes de two main advantages. First, solid compressão: 7z concatenates all arquivos em a single stream antes compressing, allowing the LZMA2 algorithm to find repeated patterns across arquivo boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each arquivo independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder em vez de Huffman coding, which more precisely models symbol probabilities e approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% menor que ZIP para software distributions.

Q: Qual é a diferença entre &quot;7z x&quot; e &quot;7z e&quot; commands?

&quot;7z x&quot; extracts com full paths — it recreates the directory structure de the archive no output location, preserving the folder hierarchy. &quot;7z e&quot; extracts everything para o current directory sem any folder structure — all arquivos land flat no destination, regardless of how they were organized no archive. If two arquivos no archive have the same name in different directories, &quot;7z e&quot; will overwrite one com the other. Always usar &quot;7z x&quot; when you querer preserve directory structure, e &quot;7z e&quot; only when you know the archive contém flat arquivos ou you intentionally want all arquivos in one directory.

Q: Why does 7z achieve better Komprimierung than ZIP even at equivalent settings?

7z&#039;s superior Komprimierung comes von two main advantages. First, solid Komprimierung: 7z concatenates all Dateien in einem single stream vor compressing, allowing the LZMA2 algorithm to find repeated patterns across Datei boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each Datei independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder anstatt Huffman coding, which more precisely models symbol probabilities und approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% kleiner als ZIP für Software distributions.

PC By Pablo Cirre • Updated May 7, 2026

What Is 7-Zip?

7-Zip is a free and open-source file archiver created by Igor Pavlov in 1999 and released under the GNU LGPL. It introduces the 7z container format, which supports very high compression ratios using the LZMA (Lempel-Ziv-Markov chain algorithm) and LZMA2 compression algorithms. 7-Zip became famous for consistently achieving 30–70% better compression than ZIP on typical software distributions.

7-Zip is cross-platform: the full GUI runs on Windows, while the command-line tool 7z (via p7zip) is available on Linux and macOS. The 7z format is specified in an open technical document, enabling independent implementations in many languages.

The 7z Format Architecture

Unlike ZIP's per-file compression, 7z uses solid compression by default — all files are concatenated and compressed as a single stream. This means:

Dramatically better compression for many small similar files (e.g., source code, log files) because the compressor can find redundancy across files.
No random access: to extract file N, you must decompress from the beginning of the solid block.
Decompressor memory: LZMA2 with large dictionary sizes (up to 4 GB) requires significant RAM on both the compressor and decompressor.

The 7z container stores:

Archive header (signature: 37 7A BC AF 27 1C)
Packed streams (compressed data blocks)
Header with file metadata (names, sizes, timestamps, checksums, permissions)

The header itself is compressed and at the end of the file (similar to ZIP's central directory), enabling streaming append.

Compression Methods in 7z

Method	Notes
LZMA	Default before 7-Zip 9.30 — dictionary up to 1.5 GB
LZMA2	Default since 7-Zip 9.30 — multi-threaded, dictionary up to 4 GB
PPMD	Statistical compression — excellent for text, competes with LZMA on English text
BZip2	Standard bzip2 — slower than LZMA, worse ratio
Deflate	zlib DEFLATE — for compatibility
Copy	Stored mode
Delta	Pre-processing filter for binary data (executable, audio, video)
BCJ / BCJ2	x86 branch conversion filter — improves compression of x86 executables by 5–15%

The most powerful configuration for software: LZMA2 + BCJ2 filter — used by major software distributors.

7z vs. ZIP: Compression Comparison

Typical results on a 100 MB software distribution (mix of executables, libraries, data):

Format	Size	Compression time	Decompression time
Uncompressed	100 MB	—	—
ZIP (Deflate, level 6)	68 MB	3 s	1 s
ZIP (Deflate, level 9)	65 MB	12 s	1 s
7z (LZMA2, level 5)	52 MB	8 s	3 s
7z (LZMA2, level 9)	48 MB	35 s	3 s
7z (LZMA2, level 9 + BCJ2)	42 MB	40 s	3 s

7z consistently achieves 20–35% smaller archives than ZIP on software. Decompression is fast even at high compression levels because LZMA2 decompression is significantly simpler than compression.

AES-256 Encryption in 7z

7z supports AES-256 encryption with a key derived from the password via SHA-256 with 524,288 iterations (making brute-force attacks expensive). Crucially, 7z encrypts filenames and directory structure too — the archive appears as a single opaque blob. This is a significant security advantage over ZIP's AES encryption.

# Encrypt with AES-256 (includes filename encryption)
7z a -mhe=on -p"strong-password" encrypted.7z files/

# -mhe=on = header encryption (encrypts filenames too)

7-Zip Command-Line Reference

# Add files to archive (create)
7z a archive.7z files/
7z a -t7z -mx=9 archive.7z files/   # max compression

# Extract
7z x archive.7z                     # extract with full paths
7z e archive.7z                     # extract to current dir (no paths)
7z x archive.7z -o/output/dir/

# List contents
7z l archive.7z

# Test integrity
7z t archive.7z

# Update (add/replace)
7z u archive.7z newfile.txt

# Delete file from archive
7z d archive.7z unwanted.txt

# Create split archive (100 MB volumes)
7z a -v100m archive.7z largefile.iso

Supported Formats (Reading)

7-Zip can open and extract from many formats beyond 7z:

Format	Read	Write
7z	✅	✅
ZIP	✅	✅
GZIP	✅	✅
BZIP2	✅	✅
XZ	✅	✅
TAR	✅	✅
RAR (v1-5)	✅	❌
ISO 9660	✅	❌
WIM	✅	✅
DMG	✅	❌
CAB	✅	❌
MSI	✅	❌
NSIS installer	✅	❌
EXE (self-extracting)	✅	✅ (7z SFX)
RPM / DEB	✅	❌
VHD / VMDK	✅	❌

This makes 7-Zip a universal archive inspector tool even when 7z is not the distribution format.

Self-Extracting Archives (SFX)

7-Zip can create self-extracting .exe files — archives that decompress themselves without requiring 7-Zip to be installed on the target machine. Useful for distributing software to end users:

# Create SFX (Windows executable)
7z a -sfx archive.exe files/

# Custom SFX with GUI configuration
7z a -sfx7z.sfx -m0=LZMA2 -mx=9 setup.exe files/

LZMA Algorithm Deep Dive

LZMA (Lempel-Ziv-Markov chain Algorithm) combines:

LZ77 dictionary matching — finds repeated strings in previous output and replaces them with (offset, length) pairs. Dictionary size determines how far back it looks (7-zip default: 16 MB; maximum: 4 GB).
Markov chain range coder — arithmetic-like coder that encodes probabilities of symbols using context models. Much more efficient than Huffman coding for non-uniform distributions.
Literal/match model — separate probability models for whether the next symbol is a literal byte or a match reference.

LZMA2 adds:

Multi-threading: splits input into chunks processed by independent LZMA streams.
Incompressible block pass-through: chunks that cannot be compressed are stored uncompressed without penalty.
Simpler container: no framing complications of LZMA (fixes the partial-flush issue).

7z in Software Ecosystems

Inno Setup: Windows installer framework — can use 7z LZMA2 compression internally.
NSIS: Nullsoft Scriptable Install System — alternative installer using 7z.
pacman (Arch Linux): uses .pkg.tar.zst (Zstandard) but historically used .pkg.tar.xz which is LZMA2.
RPM / DEB: can contain LZMA2/XZ payloads since LZMA adoption.
Wine: includes 7z for extracting Windows installers.

7z vs. RAR

Feature	7z	RAR
License	Free, open source	Proprietary (free to decompress)
Compression	LZMA2	RAR5 (128 MB dictionary)
Ratio	~Equal	Slightly worse than 7z
Encryption	AES-256 + filename encryption	AES-256 + filename encryption
Recovery records	No	Yes (parity data for corrupt archives)
Solid archives	Yes	Yes
Split archives	Yes	Yes
Reading on Linux	p7zip (7z)	unrar (free)
Cost	Free	~$40 for WinRAR (though never enforced)

Choose 7z for open-source workflows. Choose RAR only if recovery records (repair capability) are critical.

Best Practices

Use LZMA2 compression level 5 for a good speed/ratio balance; level 9 for distribution archives where compression time is acceptable.
Enable solid mode (default) for many small similar files; disable for large heterogeneous files where random access is needed.
Use -mhe=on to encrypt headers (filenames) along with content for sensitive archives.
Use strong passwords — 7z's AES-256 with 500K SHA-256 iterations is resistant to brute force only if the password is high-entropy.
Specify dictionary size (-md=256m) based on available RAM — larger dictionaries improve ratio but require RAM during decompression.
Use BCJ filter (-mf=BCJ2) when compressing executables and DLLs.
Create split volumes for archives that must be transmitted via size-limited channels.
Test archives after creation with 7z t.
Prefer 7z over RAR for open-source and cross-platform scenarios.
Use XZ (LZMA2) via TAR on Linux for package distribution — it is a streaming format without the 7z container overhead.

Related conversions

Archive format conversions used most often:

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Frequently Asked Questions

7z's superior compression comes from two main advantages. First, solid compression: 7z concatenates all files into a single stream before compressing, allowing the LZMA2 algorithm to find repeated patterns across file boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each file independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder instead of Huffman coding, which more precisely models symbol probabilities and approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% smaller than ZIP for software distributions.

7z's superior compressão comes de two main advantages. First, solid compressão: 7z concatenates all arquivos em a single stream antes compressing, allowing the LZMA2 algorithm to find repeated patterns across arquivo boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each arquivo independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder em vez de Huffman coding, which more precisely models symbol probabilities e approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% menor que ZIP para software distributions.

7z's superior Komprimierung comes von two main advantages. First, solid Komprimierung: 7z concatenates all Dateien in einem single stream vor compressing, allowing the LZMA2 algorithm to find repeated patterns across Datei boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each Datei independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder anstatt Huffman coding, which more precisely models symbol probabilities und approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% kleiner als ZIP für Software distributions.

7z's superior compresión comes de two main advantages. First, solid compresión: 7z concatenates all archivos en a single stream antes compressing, allowing the LZMA2 algorithm to find repeated patterns across archivo boundaries (e.g., the same library code appearing in multiple executables). ZIP compresses each archivo independently, losing cross-file redundancy. Second, LZMA2 algorithm: LZMA2 uses a Markov-chain range coder en vez de Huffman coding, which more precisely models symbol probabilities y approaches the theoretical information-theoretic limit more closely than DEFLATE. Typical result: 7z produces archives 20-40% más pequeño que ZIP para software distributions.

7z (LZMA2) typically beats both ZIP and RAR by 10–30% for text-heavy content, but is slower to create. RAR compresses slightly better than ZIP and supports recovery records (good for damaged archives) but the format is proprietary. ZIP is the universal lingua franca — every OS opens it natively. Use 7z for long-term storage, ZIP for sharing.

In ZIP, even with AES-256 content encryption, the filename, size, and directory structure of each file are stored unencrypted in the central directory. An attacker can learn what files are in the archive without knowing the password. In 7z, with header encryption enabled (-mhe=on), the entire header (including all filenames, sizes, timestamps, and structure) is encrypted with AES-256. The archive appears as a completely opaque binary blob to anyone without the password. This is critical for sensitive archives — if the filenames themselves reveal confidential information (medical records, financial documents), ZIP's lack of filename encryption is a real security risk.

In ZIP, even com AES-256 content encryption, o arquivoname, size, e directory structure of each arquivo are stored unencrypted no central directory. An attacker can learn what arquivos são no archive sem knowing the password. In 7z, com header encryption enabled (-mhe=on), the entire header (including all filenames, sizes, timestamps, e structure) is encrypted com AES-256. The archive appears como um completely opaque binary blob to anyone sem the password. This is critical para sensitive archives — if o arquivonames themselves reveal confidential information (medical records, financial documents), ZIP's lack of filename encryption is a real security risk.

In ZIP, even mit AES-256 content encryption, die Dateiname, size, und directory structure von each Datei are stored unencrypted im central directory. An attacker can learn what Dateien are im archive ohne knowing the password. In 7z, mit header encryption enabled (-mhe=on), the entire header (including all filenames, sizes, timestamps, und structure) is encrypted mit AES-256. The archive appears als ein completely opaque binary blob to anyone ohne the password. This is critical für sensitive archives — if die Dateinames themselves reveal confidential information (medical records, financial documents), ZIP's lack von filename encryption is a real security risk.

In ZIP, even con AES-256 content encryption, el archivoname, size, y directory structure de each archivo are stored unencrypted en el central directory. An attacker can learn what archivos are en el archive sin knowing the password. In 7z, con header encryption enabled (-mhe=on), the entire header (including all filenames, sizes, timestamps, y structure) is encrypted con AES-256. The archive appears como un completely opaque binary blob to anyone sin the password. This is critical para sensitive archives — if el archivonames themselves reveal confidential information (medical records, financial documents), ZIP's lack de filename encryption is a real security risk.

Yes, when the file contains anything sensitive. Standard ZIP "encryption" (ZipCrypto) is broken and trivially crackable. Use AES-256 (ZIP 2.0+, supported by 7-Zip, WinRAR, modern Windows). Verify the encryption type when creating: many tools default to ZipCrypto for compatibility. Better still, use 7z which uses AES-256 by default.

"7z x" extracts with full paths — it recreates the directory structure from the archive in the output location, preserving the folder hierarchy. "7z e" extracts everything to the current directory without any folder structure — all files land flat in the destination, regardless of how they were organized in the archive. If two files in the archive have the same name in different directories, "7z e" will overwrite one with the other. Always use "7z x" when you want to preserve directory structure, and "7z e" only when you know the archive contains flat files or you intentionally want all files in one directory.

"7z x" extracts com full paths — it recreates the directory structure de the archive no output location, preserving the folder hierarchy. "7z e" extracts everything para o current directory sem any folder structure — all arquivos land flat no destination, regardless of how they were organized no archive. If two arquivos no archive have the same name in different directories, "7z e" will overwrite one com the other. Always usar "7z x" when you querer preserve directory structure, e "7z e" only when you know the archive contém flat arquivos ou you intentionally want all arquivos in one directory.

"7z x" extracts mit full paths — it recreates the directory structure von the archive im output location, preserving the folder hierarchy. "7z e" extracts everything zum current directory ohne any folder structure — all Dateien land flat im destination, regardless von how they were organized im archive. If two Dateien im archive have the same name in different directories, "7z e" will overwrite one mit the other. Always verwenden "7z x" when you want to preserve directory structure, und "7z e" only when you know the archive contains flat Dateien oder you intentionally want all Dateien in one directory.

"7z x" extracts con full paths — it recreates the directory structure de the archive en el output location, preserving the folder hierarchy. "7z e" extracts everything al current directory sin any folder structure — all archivos land flat en el destination, regardless de how they were organized en el archive. If two archivos en el archive have the same name in different directories, "7z e" will overwrite one con the other. Always usar "7z x" when you want to preserve directory structure, y "7z e" only when you know the archive contains flat archivos o you intentionally want all archivos in one directory.

Original ZIP: 4 GB total + 65,535 files. ZIP64 (transparent extension): up to 16 EB and unlimited files. Modern tools (Windows Explorer, macOS Finder, 7-Zip, Linux unzip) all support ZIP64 automatically when needed. The only catch: very old tools (pre-2007) cannot open ZIP64 archives.

Disable solid mode (7z a -ms=off) when: (1) the archive will be used for random file access, since extracting one file from a solid archive requires decompressing the entire solid block before it; (2) files in the archive are large and heterogeneous (e.g., a mix of videos and documents) where cross-file redundancy is minimal; (3) you plan to update individual files frequently, since modifying any file in a solid block requires rebuilding the entire block; (4) the recipient has very limited RAM, since LZMA2 decompressing a solid block requires the full dictionary size (up to 4 GB) in memory. For distribution archives of similar files (source code, game assets), keep solid mode enabled.

Disable solid mode (7z a -ms=off) when: (1) the archive will be used para random arquivo access, since extracting one arquivo de a solid archive requires decompressing the entire solid block antes it; (2) arquivos no archive are large e heterogeneous (e.g., a mix of videos e documents) where cross-file redundancy is minimal; (3) you plan to update individual arquivos frequently, since modifying any arquivo em um solid block requires rebuilding the entire block; (4) the recipient has very limited RAM, since LZMA2 decompressing a solid block requires the full dictionary size (up to 4 GB) in memory. para distribution archives of similar arquivos (source code, game assets), keep solid mode enabled.

Disable solid mode (7z a -ms=off) when: (1) the archive will be used für random Datei access, since extracting one Datei von a solid archive requires decompressing the entire solid block vor it; (2) Dateien im archive are large und heterogeneous (e.g., a mix von videos und documents) where cross-file redundancy is minimal; (3) you plan to update individual Dateien frequently, since modifying any Datei in einem solid block requires rebuilding the entire block; (4) the recipient has very limited RAM, since LZMA2 decompressing a solid block requires the full dictionary size (up to 4 GB) in memory. für distribution archives von similar Dateien (source code, game assets), keep solid mode enabled.

Disable solid mode (7z a -ms=off) when: (1) the archive will be used para random archivo access, since extracting one archivo de a solid archive requires decompressing the entire solid block antes it; (2) archivos en el archive are large y heterogeneous (e.g., a mix de videos y documents) where cross-file redundancy is minimal; (3) you plan to update individual archivos frequently, since modifying any archivo en un solid block requires rebuilding the entire block; (4) the recipient has very limited RAM, since LZMA2 decompressing a solid block requires the full dictionary size (up to 4 GB) in memory. para distribution archives de similar archivos (source code, game assets), keep solid mode enabled.

Some content does not compress well: already-compressed media (JPG, MP4, MP3), encrypted files, random binary data. Compression algorithms exploit redundancy — these formats already removed it. To shrink them you would need lossy re-encoding, not archiving. Save archives for text, source code, uncompressed media (BMP, WAV, RAW), and document files.