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# Resetting an Engine

## Overview

[`Engine.reset`](/docs/engine/reset) removes installed overrides. Reset one slot when replacing a
provider completely, or omit the slot to restore every cryptographic primitive to Viem's defaults.

## Recipes

### Reset One Slot

Reset a slot before installing another provider when primitives omitted by the new provider should
not remain installed.

```ts twoslash
import { Engine } from 'viem'
import { Engine as NodeEngine } from 'viem/node'

Engine.reset('Hash') // [!code focus]

const { Hash } = await NodeEngine.engine()
await Engine.install({ Hash })
```

### Reset Every Slot

Restore Viem's default implementations between tests or isolated application runs.

```ts twoslash
import { Engine } from 'viem'

Engine.reset() // [!code focus]
```

## `Engine.reset`

Restores one slot or the complete Engine to its default implementations.

### Usage

```ts twoslash
import { Engine } from 'viem'

Engine.reset('Hash')
Engine.reset()
```

### Definition

```ts
function reset(slot?: keyof Engine.Engine): void
```

### Parameters

#### slot

* **Type:** `keyof Engine.Engine`
* **Optional**

The slot to reset. When omitted, every slot is reset.

```ts twoslash
import { Engine } from 'viem'
// ---cut---
Engine.reset('Hash') // [!code focus]
```

### Return Value

`void`

No value is returned.

### Errors

| Error | Description |
| --- | --- |
| [`Engine.UnknownSlotError`](/docs/engine/errors#engineunknownsloterror) | `slot` is not a recognized Engine slot. |