# Built-in Hooks

prek includes fast, Rust-native implementations of popular hooks for speed and low overhead.

Use `repo: builtin` to select them directly, or keep a supported remote hook config and let prek use its automatic fast path.

|  | `repo: builtin` | Automatic fast path |
| --- | --- | --- |
| Config remains usable by upstream `pre-commit` | No | Yes |
| Remote repository and manifest | Not used | Cloned at the pinned `rev` |
| Environment available for fallback | Not needed | Yes |
| Network needed for first preparation | No | Yes |
| How to opt out | Replace `repo: builtin` with a remote or local hook | Set the hook's declared language or `PREK_NO_FAST_PATH=1` |

> [!NOTE]
>
> **Check implementation notes when behavior matters**
>
> The Rust implementations target the same purpose as their upstream hooks, but a hook can have documented differences in arguments, defaults, or edge cases. Check its entry in the [Hook Reference](<https://prek.j178.dev/0.5.6/reference/built-in-hooks/#hook-reference>). To compare behavior, disable the fast path and run the pinned implementation.

## Use built-in hooks directly

Add `repo: builtin` and select hooks by ID:

```toml
[[repos]]
repo = "builtin"
hooks = [
  { id = "trailing-whitespace" },
  { id = "check-added-large-files" },
]
```

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

List the builtins bundled with your installed prek version using:

```bash
prek util list-builtins
```

See the [built-in hook reference](<https://prek.j178.dev/0.5.6/reference/built-in-hooks/index.md>) for the complete list of hooks, supported arguments, and behavior notes.

## Use the automatic fast path

For supported hooks from `https://github.com/pre-commit/pre-commit-hooks`, prek runs the built-in implementation automatically. Your existing remote config can stay compatible with upstream pre-commit. The `rev` field does not affect fast-path detection. It still selects the manifest that prek reads and the repository implementation used for fallback.

```yaml
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks  # Enables fast path
    rev: v6.0.0  # Used for the manifest and fallback, not 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.

See [fast-path support](<https://prek.j178.dev/0.5.6/reference/built-in-hooks/#automatic-fast-path>) for the list of hooks that use the built-in implementation automatically. Other hooks run via the standard method.

### Run the repository implementation

To use the pinned repository implementation for a single hook, explicitly set the language declared by that hook:

```yaml
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v6.0.0
    hooks:
      - id: check-yaml
        language: python  # Use the pinned repository implementation
```

To disable the fast path for every hook in a prek invocation:

```bash
PREK_NO_FAST_PATH=1 prek run
```