---
id: isal
version: "1.8.0"
license: PSF-2.0
license_treatment: permissive
maintenance: active
---

# isal — Faster zlib and gzip compatible compression and decompression by providing python bindings for the ISA-L ibrary.

License: permissive · Maintenance: active · Downloads: 2.8M/mo

## What it is and what it does

python-isal wraps Intel's ISA-L (Intelligent Storage Acceleration Library) to provide faster compression and decompression than Python's standard zlib and gzip modules. It offers four main modules: isal_zlib (zlib replacement), igzip (gzip replacement), igzip_threaded (for multi-threaded streaming I/O that escapes the GIL), and igzip_lib (direct access to ISA-L's compression API). The library implements key algorithms in assembly language for speed while maintaining near-complete API compatibility with the standard library.

The package is designed as a drop-in replacement, so existing code using zlib or gzip can often switch to isal_zlib or igzip with minimal changes. However, there are intentional differences: compression levels are 0–3 instead of 1–9, flush modes are limited, and memory level mapping differs. These trade-offs reflect ISA-L's design and are documented to help developers understand when and how to adopt the library.

Use it for:

- Replace zlib in data pipeline code to accelerate compression without rewriting application logic
- Stream large compressed files using igzip_threaded to parallelize I/O and bypass Python's GIL
- Build bioinformatics or data-heavy tools that compress/decompress frequently and need lower latency
- Implement gzip-compatible command-line compression tools via the igzip module or CLI
- Reduce CPU cost in production services that compress logs, backups, or API responses at scale

## Worth the install?

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

Provides Python bindings for Intel's ISA-L library to accelerate zlib and gzip compression and decompression with drop-in replacement modules.

Yes, if you compress or decompress data frequently and can tolerate the compression-level API differences. The library is production-stable (active maintenance, no known vulnerabilities, permissive license), offers genuine performance gains via assembly-level optimization, and provides both synchronous and threaded I/O options. Install friction is moderate but manageable with pre-built wheels for common platforms. Not necessary if your compression workload is negligible or if you require exact zlib/gzip API compatibility.

## Install

pip install isal
uv add isal
poetry add isal

## Installing isal

Before you install: Medium install friction: compiled wheels available for Python 3.10–3.13 on x86_64, aarch64, and ARM macOS, plus Windows; requires Python 3.9+. Repository is active with recent commits and no known vulnerabilities.

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

Quickstart:

pip install isal

from isal import isal_zlib, igzip

# Use as drop-in replacement for zlib
compressed = isal_zlib.compress(b'data')
decompressed = isal_zlib.decompress(compressed)

# Or use igzip as gzip replacement
with igzip.open('file.gz', 'wb') as f:
    f.write(b'data')

Compression levels range 0–3 (not 1–9 like zlib); level 0 means lowest compression, not no compression. Requires ISA-L build dependencies for development.

Verify before relying:

- Whether performance gains justify medium install friction for your specific workload
- Compatibility of memory level mapping (1–9 range) with existing zlib code in production

## Package facts

- License: PSF-2.0 (permissive)
- Python support: supports_current
- Install friction: medium
- Maintenance: active
- Downloads: 2.8M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

fast gzip compression python, zlib acceleration, isa-l python bindings, high-performance compression, igzip module, threaded compression streaming, deflate acceleration, compression, performance-optimization, assembly-accelerated

[View on SkillFed](https://skillfed.io/packages/isal) · [View on PyPI](https://pypi.org/project/isal/)