Project Summary
zlib is designed to be a free, general-purpose, legally unencumbered -- that is, not covered by any patents -- lossless data-compression library for use on virtually any computer hardware and operating system. The zlib data format is itself portable across platforms. Unlike the LZW compression method used in Unix compress(1) and in the GIF image format, the compression method currently used in zlib essentially never expands the data. (LZW can double or triple the file size in extreme cases.) zlib's memory footprint is also independent of the input data and can be reduced, if necessary, at some cost in compression.
In a Nutshell, zlib...
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has a well established, mature codebase
maintained by a large development team
with stable Y-O-Y commits -
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took an estimated 10 years of effort (COCOMO model)
starting with its first commit in July, 2010
ending with its most recent commit 4 months ago
Quick Reference
zlib License (aka zlib/libpng)
Permitted
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These details are provided for information only. No information here is legal advice and should not be used as such.
Project Security
Vulnerabilities per Version ( last 10 releases )
Project Vulnerability Report
Security Confidence Index
Vulnerability Exposure Index
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30 Day SummaryMay 12 2026 — Jun 11 2026
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12 Month SummaryJun 11 2025 — Jun 11 2026
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