isal
Faster zlib and gzip compatible compression and decompression by providing python bindings for the ISA-L ibrary.
Decision gist · record as of 2026-08-14
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.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- 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.
- 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+.
License · maintenance · safety
PSF-2.0 (permissive) — Licensed under PSF-2.0 (permissive), allowing use in proprietary and open-source projects without significant restrictions.
last release 2025-09-10 (338 days) · last repo commit 2026-07-29 · 58 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 2,787,014 downloads/mo, #2,891 on PyPI
Alternatives
Verify before relying
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')- 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
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 on this page. Verify before relying on it.
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
isal on PyPI
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.
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.
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')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 the current Python release >=3.9 |
| Install friction | Medium. Platform-specific wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 338 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 2,787,014 / month, #2,891 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableOperating System :: MacOSOperating System :: Microsoft :: WindowsOperating System :: POSIX :: LinuxProgramming Language :: CProgramming Language :: Python :: 3Programming Language :: Python :: 3 :: OnlyProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: System :: Archiving :: Compression |
Evidence: isal-1.8.0-cp310-cp310-macosx_10_9_x86_64.whl; isal-1.8.0-cp310-cp310-macosx_11_0_arm64.whl; isal-1.8.0-cp310-cp310-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; isal-1.8.0-cp310-cp310-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl; isal-1.8.0-cp310-cp310-musllinux_1_2_aarch64.whl; isal-1.8.0-cp310-cp310-musllinux_1_2_x86_64.whl; isal-1.8.0-cp310-cp310-win_amd64.whl; isal-1.8.0-cp311-cp311-macosx_10_9_x86_64.whl; isal-1.8.0-cp311-cp311-macosx_11_0_arm64.whl; isal-1.8.0-cp311-cp311-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; isal-1.8.0-cp311-cp311-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl; isal-1.8.0-cp311-cp311-musllinux_1_2_aarch64.whl; isal-1.8.0-cp311-cp311-musllinux_1_2_x86_64.whl; isal-1.8.0-cp311-cp311-win_amd64.whl; isal-1.8.0-cp312-cp312-macosx_10_13_x86_64.whl; isal-1.8.0-cp312-cp312-macosx_11_0_arm64.whl; isal-1.8.0-cp312-cp312-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; isal-1.8.0-cp312-cp312-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl; isal-1.8.0-cp312-cp312-musllinux_1_2_aarch64.whl; isal-1.8.0-cp312-cp312-musllinux_1_2_x86_64.whl
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