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Environment Variable Reference

prek supports the following environment variables:

prek variables

PREK_HOME

Override the prek data directory (caches, toolchains, hook envs). If beginning with ~, it is expanded to the user's home directory. Defaults to ~/.cache/prek on macOS and Linux, and %LOCALAPPDATA%\prek on Windows.

PREK_COLOR

Control colored output: auto (default), always, or never.

PREK_QUIET

Control quiet output mode. Set to 1 for quiet mode (equivalent to -q, only shows failed hooks), or 2 for silent mode (equivalent to -qq, no output to stdout).

PREK_SKIP

Comma-separated list of hook IDs to skip (e.g. black,ruff). See Skipping Projects or Hooks for details.

PREK_ALLOW_NO_CONFIG

Allow running without a configuration file (useful for ad-hoc runs).

PREK_NO_CONCURRENCY

Disable parallelism for installs and runs. If set, force concurrency to 1.

PREK_MAX_CONCURRENCY

Set the maximum number of concurrent hooks (minimum 1). Defaults to the number of CPU cores when unset. Ignored when PREK_NO_CONCURRENCY is set. If you encounter "Too many open files" errors, lowering this value or raising the file descriptor limit with ulimit -n can help.

PREK_NO_FAST_PATH

Disable Rust-native built-in hooks; always use the original hook implementation. See Built-in Fast Hooks for details.

PREK_UV_SOURCE

Control how uv (Python package installer) is installed. Options:

  • github (download from GitHub releases)
  • pypi (install from PyPI)
  • tuna (use Tsinghua University mirror)
  • aliyun (use Alibaba Cloud mirror)
  • tencent (use Tencent Cloud mirror)
  • pip (install via pip)
  • a custom PyPI mirror URL

If not set, prek automatically selects the best available source.

PREK_NATIVE_TLS

Use the system trusted store instead of the bundled webpki-roots crate.

PREK_CONTAINER_RUNTIME

Specify the container runtime to use for container-based hooks (e.g., docker, docker_image). Options:

  • auto (default, auto-detect available runtime)
  • docker
  • podman
  • container (Apple's Container runtime on macOS, see container)

PREK_LOG_TRUNCATE_LIMIT

Control the truncation limit for command lines shown in trace logs (Executing ...). Defaults to 120 characters of arguments; set a larger value to reduce truncation.

PREK_RUBY_MIRROR

Override the Ruby installer base URL used for downloaded Ruby toolchains (for example, when using mirrors or air-gapped CI environments). See Ruby language support for details.

PREK_RUST_PROFILE

Override the rustup profile used when installing managed Rust toolchains (minimal, default, or complete). Defaults to minimal. Set to default to include rustfmt and clippy. See Rust language support for details.

Compatibility fallbacks

PRE_COMMIT_ALLOW_NO_CONFIG

Fallback for PREK_ALLOW_NO_CONFIG.

PRE_COMMIT_NO_CONCURRENCY

Fallback for PREK_NO_CONCURRENCY.

SKIP

Fallback for PREK_SKIP.