---
id: zlib-ng
version: "1.0.0"
license: PSF-2.0
license_treatment: permissive
maintenance: active
---

# zlib-ng — Drop-in replacement for zlib and gzip modules using zlib-ng

License: permissive · Maintenance: active · Downloads: 1.8M/mo

## What it is and what it does

zlib-ng wraps the zlib-ng C library to provide faster compression and decompression than Python's built-in zlib and gzip modules. It offers three modules: zlib_ng (a zlib replacement), gzip_ng (a gzip replacement), and gzip_ng_threaded (which adds multi-threaded streaming for large files). All three are designed to be nearly drop-in replacements for their standard library counterparts, with the same API and behavior—the main difference is speed. The package includes a command-line tool (python -m zlib_ng.gzip_ng) that mimics the standard gzip utility.

The package is built from C extensions and requires compilation or platform-specific wheels during installation. It supports Linux, macOS, and Windows across multiple architectures. There are minor differences from the standard library: compression level 1 produces worse compression ratios than standard zlib, and gzip_ng.open returns GzipNGFile instead of GzipFile (though GzipFile is aliased for compatibility). No runtime dependencies are required once installed.

Use it for:

- Replace zlib in data processing pipelines where compression speed is a bottleneck and standard library performance is insufficient.
- Accelerate gzip-based file I/O in applications that read or write many compressed files.
- Stream large compressed files using gzip_ng_threaded to parallelize I/O and escape Python's GIL.
- Implement gzip-compatible command-line compression tools with better performance than the standard gzip utility.
- Reduce latency in HTTP compression workflows where zlib is the bottleneck in request/response handling.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Provides faster zlib and gzip compression and decompression by wrapping the zlib-ng library with Python bindings that serve as drop-in replacements for the standard library modules.

Yes, if you need faster compression/decompression and can tolerate medium install friction (compiled wheels). The package is actively maintained, has no known vulnerabilities, is permissively licensed, and offers a true drop-in replacement API. Install only if your workload is actually bottlenecked on compression—the standard library zlib is sufficient for most use cases.

## Install

pip install zlib-ng
uv add zlib-ng
poetry add zlib-ng

## Installing zlib-ng

Before you install: Medium install friction due to compiled C extensions requiring platform-specific wheels. Wheels are available for common platforms (Linux x86_64/aarch64, macOS x86_64/arm64, Windows x64) across Python 3.10–3.12, with active maintenance and no runtime dependencies.

License in practice: Licensed under PSF-2.0 (permissive), allowing use in most projects without significant restrictions.

Quickstart:

pip install zlib-ng

from zlib_ng import zlib_ng
compressed = zlib_ng.compress(b'data')
decompressed = zlib_ng.decompress(compressed)

Requires Python 3.9 or later; platform-specific wheels may not be available for all architectures.

Verify before relying:

- Actual performance improvement magnitude compared to standard library zlib across different workloads and compression levels.
- Full compatibility surface with standard library zlib and gzip beyond the documented minor differences.
- Support status for Python 3.13 and 3.14 (listed in classifiers but not in wheel evidence).

## Package facts

- License: PSF-2.0 (permissive)
- Python support: supports_current
- Install friction: medium
- Maintenance: active
- Downloads: 1.8M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

fast zlib compression, gzip performance replacement, zlib-ng python bindings, accelerated deflate compression, drop-in zlib replacement, compression, performance-optimization

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