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python-build-standalone: Pre-built Python Distributions

by Tim Hopper · Markdown

python-build-standalone is a project that produces self-contained, portable CPython distributions for macOS, Linux, and Windows. Gregory Szorc created the project; Astral, now part of OpenAI, maintains it. When uv runs uv python install, the binary it downloads comes from python-build-standalone.

Most developers interact with python-build-standalone indirectly through uv. The project matters when debugging platform-specific interpreter issues or understanding where managed Python installations come from.

What the distributions contain

Each distribution is a complete CPython installation: the interpreterThe program that reads and executes Python code. When you run "python3 hello.py", python3 is the interpreter. , the standard library, header files for building C extensions, and pip. Dependencies like OpenSSL, SQLite, and zlib are statically linked or bundled, so the distributions need only a C library (glibc or musl on Linux) from the host system.

The install-only archives that uv downloads use the fastest available build configuration (typically PGO+LTO optimized) and weigh 30-60 MB compressed per platform.

Platform and architecture coverage

Platform Architectures
macOS x86-64, ARM64 (Apple Silicon)
Linux (glibc) x86-64, ARM64, and x86-64 microarchitecture tiers (v2, v3, v4)
Linux (musl) x86-64, ARM64
Windows x86-64, ARM64 (Python 3.11+)

Linux glibc builds target glibc 2.17 or newer, covering most distributions released after 2014. The x86-64 microarchitecture tiers (v2, v3, v4) use newer CPU instruction sets for better performance; the baseline x86-64 build maximizes portability.

Build variants

A single CPython version ships in several configurations:

  • PGO+LTO is the default for install-only archives. Profile-guided optimization and link-time optimization produce the fastest interpreter.
  • Free-threaded builds (CPython 3.13+) remove the GIL. uv installs them with the t suffix: uv python install 3.14t.
  • Debug builds include runtime assertions and are useful for extension module development.
  • Static musl builds link everything statically, producing a fully self-contained binary that cannot load dynamically linked C extensions.

Downstream consumers

python-build-standalone is the Python distribution source for:

  • uv (automatic download on uv python install and uv run)
  • mise (default Python backend)
  • Rye (predecessor to uv’s Python management)
  • Bazel rules_python (hermetic Python toolchains)
  • PyApp (self-contained application launchers)

How uv uses the distributions

uv maintains a catalog of available python-build-standalone releases. uv python install 3.14 resolves to the latest patch release for that minor version, downloads the PGO+LTO install-only archive for the current platform, and unpacks it to ~/.local/share/uv/python/ (or %APPDATA%\uv\python\ on Windows). Subsequent uv run and uv sync commands select a managed interpreter automatically when it satisfies the project’s requires-python.

List installed managed interpreters with:

uv python list --managed-python --only-installed

Known limitations

  • musl/Alpine compatibility. Dynamically linked musl builds work on Alpine Linux but cannot load glibc-based C extensions. Fully static musl builds cannot load any dynamically linked extensions. This affects packages with C components like NumPy or cryptography.
  • Build-time path references. Some build artifacts retain references to the original build-time paths. This rarely matters in practice but can surface when building C extensions that inspect sysconfig paths.
  • libedit instead of readline on Linux. Linux distributions bundle libedit rather than GNU readline, which can cause minor differences in REPL key bindings and history behavior.
  • 32-bit ARM. Builds exist for armv7 (Raspberry Pi), but uv’s libc detection has had issues on some 32-bit ARM setups. See How to install uv on 32-bit Raspberry Pi OS.

Cons

  • Not a package manager. python-build-standalone only produces interpreter binaries. Installing packages, managing virtual environments, and resolving dependencies requires a separate tool like uv or pip.
  • Larger than system packages. A bundled distribution includes OpenSSL, SQLite, and other libraries that a system package manager would share across programs.
  • Release lag. New CPython patch releases appear in python-build-standalone within days, not hours. A uv python install command may briefly resolve to the previous patch while the new build is in progress.
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