# madler/zlib

A massively spiffy yet delicately unobtrusive compression library.

Repository: https://github.com/madler/zlib
Canonical: https://ross.abutalabs.com/products/zlib
Homepage: http://zlib.net/
Language: C
License: NOASSERTION
License Family: other
Last push: 2026-06-01T09:13:57+00:00

## Health v2 (maintenance only)
Score: 72/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 85, release rhythm 39, longevity 100
- inputs: {"age_days": 5471, "days_push": 93, "days_rel": 197, "gap_med": null, "n_releases_24m": 1}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 7048, forks 2842 (observed 2026-08-28T04:09:55.427953+00:00)

## What it is
zlib is a general-purpose, patent-free data compression library written in C, implementing the zlib, deflate (RFC 1951), and gzip (RFC 1952) formats. It is the de facto standard compression library embedded in countless applications, languages, and file formats such as PNG and PDF.

## Use cases
- compress and decompress data in memory with deflate
- read and write gzip files
- decompress Flate streams inside PDF files
- add lossless compression to a C or C++ application
- implement zip file support via minizip
- exchange compressed data between big-endian and little-endian systems

## When to choose
- you need a mature, widely portable, patent-free compression library
- you must interoperate with gzip, PNG, PDF, HTTP, or zip formats
- you need a small, fast C library with bindings in nearly every language

## When to avoid
- you need the highest compression ratios, where zstd, xz/LZMA, or brotli may outperform it
- you need archive features like encryption or solid compression
- you want a modern API with built-in multithreaded compression

## Facets
- artifact type: library
- maturity: stable
- function: compression, file-system, developer-tools
- domain: developer-tools, files, cross-platform
- platform: cross-platform, c, windows, cli
- tags: deflate, gzip, zlib-format, rfc1951, lossless-compression, c-library, linux, macos

## Member repositories
- madler/zlib (main) score 72

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:09:55.427953+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T17:40:32.165684+00:00, confidence not recorded.
  - readme: https://github.com/madler/zlib (fetched 2026-08-28T04:09:55.427953+00:00, sha 9cf33e8945e3)
  - homepage: http://zlib.net/ (fetched 2026-08-29T08:36:17.751348+00:00, sha 2e77004fe5e8)
  - site_page: http://zlib.net/zlib_faq.html (fetched 2026-08-29T08:36:17.762344+00:00, sha d6d9c7a84e82)
- Data as of 2026-08-30T08:39:29.467469+00:00.