Archives & Compression (ZIP/RAR)

An encyclopedic reference on archive file formats (ZIP, RAR, 7z, TAR, gzip) and the lossless data-compression concepts behind them, covering how the formats and algorithms work, their history, and practical use for backup and file transfer. Vendor-neutral and standards-first, grounded in public specifications rather than product marketing.

3 live pages · long-term capacity 26–44

Entities

format

ZIP · RAR · 7z · TAR · gzip · bzip2 · Zstandard · Brotli

standard

DEFLATE · PKWARE APPNOTE · RFC 1951 (DEFLATE) · RFC 1952 (gzip) · ISO/IEC 21320-1

concept

LZ77 · Huffman coding · LZMA · CRC-32

product

PKZIP · 7-Zip

organization

Info-ZIP

Connected clusters

In the archive

Pages in this cluster

Planned coverage

What Is a ZIP File? — Defines the ZIP container format, what it stores, and how it bundles plus compresses multiple files into one archive.
What Is a RAR File? — Explains the proprietary RAR archive format, its typical uses, and why it needs specific software to create and open.
What Is the 7z Format? — Describes the open 7z format and its association with the 7-Zip tool, including its use of LZMA-family compression.
What Is a TAR Archive? — Explains TAR as a Unix bundling format that stores files without compressing, and why it is paired with gzip or bzip2.
What Is gzip? — Covers the gzip format and its DEFLATE-based single-stream compression as defined in RFC 1952.
What Is File Compression? — Foundational explainer distinguishing archiving from compression and introducing lossless data reduction.
Lossless vs. Lossy Compression — Contrasts the two families of compression and explains why archive formats are strictly lossless.
How DEFLATE Compression Works — Explains the DEFLATE algorithm (RFC 1951) as the combination of LZ77 dictionary matching and Huffman coding.
LZ77 and Dictionary-Based Compression — Describes how sliding-window dictionary methods replace repeated byte sequences with back-references.
Huffman Coding Explained — Introduces entropy coding and how variable-length codes shorten frequently occurring symbols.
The History of the ZIP Format — Traces ZIP from PKWARE's PKZIP and the public APPNOTE specification to its role as a universal container.
ZIP vs. RAR: How the Formats Differ — Vendor-neutral comparison of open ZIP versus proprietary RAR across openness, tooling, and features like solid archives.
Understanding Compression Ratios — Explains what a compression ratio measures and why results depend heavily on the input data's redundancy.
What Is a Checksum? — Explains CRC-32 and integrity checks stored in archives to detect corruption during storage or transfer.
How ZIP Encryption Works — Describes legacy ZipCrypto versus AES-based encryption for password-protected ZIP archives, at a conceptual level.
What Is a Solid Archive? — Explains solid compression in RAR and 7z, where files are treated as one stream to improve ratio, with its trade-offs.
Self-Extracting Archives Explained — Describes SFX archives that bundle an extractor executable, and the portability and safety considerations involved.
Multi-Volume and Split Archives — Explains splitting large archives into numbered volumes for size-limited media or transfer, and how they rejoin.
tar.gz and Tarballs Explained — Explains the common tar.gz/tgz combination of TAR bundling plus gzip compression widely used on Unix systems.
What Is Zstandard (zstd)? — Introduces the modern zstd lossless algorithm, its dictionary approach, and where it fits among older formats.
Compressing Files for Email and Transfer — Practical, tool-neutral workflow for archiving multiple files to share, with notes on size limits and integrity.
Using Archives for Backups — Explains how archive formats support backup by consolidating files, preserving structure, and verifying integrity.
What Is bzip2? — Covers bzip2's Burrows-Wheeler-transform approach and how it differs from DEFLATE-based gzip.
Common Archive Formats Compared — Overview page mapping ZIP, RAR, 7z, TAR, and gzip by openness, compression method, and typical platform.