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Built-in Fast Hooks

Prek includes fast, Rust-native implementations of popular hooks for speed and low overhead. These hooks are bundled directly into the prek binary, eliminating the need for external interpreters like Python for these specific checks.

Built-in hooks come into play in two ways:

  1. Automatic Fast Path: Automatically replacing execution for known remote repositories.
  2. Explicit Builtin Repository: Using repo: builtin for offline, zero-setup hooks.

1. Automatic Fast Path

When you use a standard configuration pointing to a supported repository (like https://github.com/pre-commit/pre-commit-hooks), prek automatically detects this and runs its internal Rust implementation instead of the Python version defined in the repository.

The fast path is activated when the repo URL matches https://github.com/pre-commit/pre-commit-hooks. No need to change anything in your configuration. Note that the rev field is ignored for detection purposes.

This provides a speed boost while keeping your configuration compatible with the original pre-commit tool.

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks  # Enables fast path
    rev: v4.5.0  # This is ignored for fast path detection
    hooks:
      - id: trailing-whitespace

Note

In this mode, prek will still clone the repository and create the environment (e.g., a Python venv) to ensure full compatibility and fallback capabilities. However, the actual hook execution bypasses the environment and runs the native Rust code.

Supported Hooks

Currently, only part of hooks from https://github.com/pre-commit/pre-commit-hooks is supported. More popular repositories may be added over time.

https://github.com/pre-commit/pre-commit-hooks

  • trailing-whitespace (Trim trailing whitespace)
  • check-added-large-files (Prevent committing large files)
  • end-of-file-fixer (Ensure newline at EOF)
  • fix-byte-order-marker (Remove UTF-8 byte order marker)
  • check-json (Validate JSON files)
  • check-toml (Validate TOML files)
  • check-yaml (Validate YAML files)
  • check-xml (Validate XML files)
  • mixed-line-ending (Normalize or check line endings)
  • check-symlinks (Check for broken symlinks)
  • check-merge-conflict (Check for merge conflicts)
  • detect-private-key (Detect private keys)
  • no-commit-to-branch (Prevent committing to protected branches)
  • check-executables-have-shebangs (Ensures that (non-binary) executables have a shebang)

Notes

  • check-yaml fast path does not yet support the --unsafe flag; for those cases, the automatic fast path is skipped.
  • Other hooks from the repository will run using the standard pre-commit behavior.

Disabling the fast path

If you need to compare with the original behavior or encounter differences:

PREK_NO_FAST_PATH=1 prek run

This forces prek to fall back to the standard execution path.

2. Explicit Builtin Repository

You can explicitly tell prek to use its internal hooks by setting repo: builtin.

This mode has significant benefits:

  • No network required: Does not clone any repository.
  • No environment setup: Does not create Python environments or install dependencies.
  • Maximum speed: Instant startup and execution.

Note: Configurations using repo: builtin are not compatible with the standard pre-commit tool.

repos:
  - repo: builtin
    hooks:
      - id: trailing-whitespace
      - id: check-added-large-files

Supported Hooks

For repo: builtin, the following hooks are supported:

  • trailing-whitespace (Trim trailing whitespace)
  • check-added-large-files (Prevent committing large files)
  • end-of-file-fixer (Ensure newline at EOF)
  • fix-byte-order-marker (Remove UTF-8 byte order marker)
  • check-json (Validate JSON files)
  • check-toml (Validate TOML files)
  • check-yaml (Validate YAML files)
  • check-xml (Validate XML files)
  • mixed-line-ending (Normalize or check line endings)
  • check-symlinks (Check for broken symlinks)
  • check-merge-conflict (Check for merge conflicts)
  • detect-private-key (Detect private keys)
  • no-commit-to-branch (Prevent committing to protected branches)
  • check-executables-have-shebangs (Ensures that (non-binary) executables have a shebang)