---
id: awscrt
version: "0.36.2"
license: Apache-2.0
license_treatment: permissive
maintenance: active
---

# awscrt — A common runtime for AWS Python projects

License: permissive · Maintenance: active · Downloads: 19.7M/mo

## What it is and what it does

awscrt is a Python wrapper around AWS's native Common Runtime library, written in C. It exposes low-level primitives for networking, TLS, event loops, and cryptographic operations that underpin AWS SDKs and tools. The package requires Python 3.8+ and ships as precompiled wheels for macOS, Linux (x86_64 and ARM), Windows, and musl-based systems.

The library uses platform-native TLS backends: Schannel on Windows, Apple Secure Transport (or optionally s2n-tls) on macOS, and s2n-tls on Linux. It bundles its own copy of libcrypto to avoid system OpenSSL dependencies. Key constraint: it uses background threads, making it incompatible with os.fork() on POSIX systems—multiprocessing must be configured to use 'spawn' or 'forkserver' instead of the default 'fork' mode.

Use it for:

- Building AWS SDK clients that require high-performance, native-code networking and TLS
- Integrating cryptographic primitives (ED25519, hashing, signing) into AWS-adjacent applications
- Deploying AWS tools in environments where pure-Python implementations are too slow
- Configuring advanced TLS behavior (e.g., enabling TLS 1.3 on macOS via environment variable)
- Debugging AWS service communication via hierarchical logging integrated with Python's logging module

## Worth the install?

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

Python bindings for the AWS Common Runtime, providing low-level networking, cryptography, and I/O primitives for AWS SDK operations.

Yes, if you are building or using AWS SDKs in Python and need the native runtime they depend on. Install friction is moderate due to compiled extensions, but wheels are well-distributed. No security vulnerabilities reported. Active maintenance and permissive Apache-2.0 license pose no barriers. Main gotcha: incompatible with os.fork() by default—requires multiprocessing configuration if you use ProcessPoolExecutor or similar.

## Install

pip install awscrt
uv add awscrt
poetry add awscrt

## Installing awscrt

Before you install: Medium install friction due to compiled C extensions across multiple platforms (macOS, Linux, Windows, ARM). Actively maintained with recent releases; no runtime dependencies simplifies deployment once installed.

License in practice: Licensed under Apache-2.0 (permissive), allowing use in commercial and proprietary projects with minimal restrictions.

Quickstart:

pip install awscrt

from awscrt.logging import init_logging, CRT_LOG_FORMAT
import logging

handler = logging.StreamHandler()
handler.setFormatter(logging.Formatter(CRT_LOG_FORMAT))
logging.getLogger('awscrt').addHandler(handler)
init_logging(logging.DEBUG)

Requires Python 3.8+. On POSIX systems (except macOS), multiprocessing defaults to 'fork', which is unsafe with awscrt's background threads—use 'spawn' or 'forkserver' context if using ProcessPoolExecutor or similar.

Verify before relying:

- Whether prebuilt wheels cover all target deployment platforms and Python versions in your environment
- Performance characteristics compared to pure-Python AWS SDK implementations
- Compatibility with specific AWS services or SDK versions that depend on this runtime

## Package facts

- License: Apache-2.0 (permissive)
- Python support: supports_current
- Install friction: medium
- Maintenance: active
- Downloads: 19.7M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

AWS common runtime python, aws-crt bindings, AWS networking library, low-level AWS SDK primitives, AWS cryptography bindings, AWS I/O event loop, AWS TLS networking, aws-sdk, networking, cryptography

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