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.

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.