A massively spiffy yet delicately unobtrusive compression library.
I feel obliged to point this out here:
Do not build zlib with the optimized assembly code.
The "hand-optimized" assembly code is a contribution and does not receive support by the library authors. There are bugs in there and it will read/write out of bounds given just the right data - we've been bit by it. Note .
The Makefiles get this right - they stay far away from any hand-rolled assembly. But the contributed Visual Studio solutions default to building with the ASM:  . *Make sure to choose Debug/ReleaseWithoutAsm.
You can check any zlib build for whether it was built with ASM via (zlibCompileFlags() & (1 << 9)): 
Needless to say, an OOB in a library as fundamental (and as user-data-facing) as zlib is a serious vulnerability. We didn't find any distribution or major software that uses a vulnerable zlib build, but if you are on Windows you might accidentally make one. Beware!
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Cloudflare fork of zlib with massive performance improvements (by cloudflare)
zlib replacement with optimizations for "next generation" systems.
Heavily optimized library for DEFLATE/zlib/gzip compression and decompression
Going away from Zlib proper but staying with its format, there’s libdeflate, an implementation that’s substantially faster on modern machines but can’t stream, and of course Zopfli, a glacially slow compressor that’s somewhat better (and occasionally much more so).
Re: Zlib memory corruption on deflate (i.e. compress)
4 projects | news.ycombinator.com | 28 Mar 2022
Release 2.0.0 - First stable release · zlib-ng/zlib-ng
1 project | reddit.com/r/programming | 19 Mar 2021
Storing State in the URL
2 projects | news.ycombinator.com | 12 May 2022
Browsers can do that?
10 projects | dev.to | 9 Feb 2022
Zstandard RFC 8878
2 projects | news.ycombinator.com | 19 Nov 2021