> **Can't find what you're looking for?** Use `search_docs` on the docs MCP server at `https://v3.viem.sh/api/mcp` to find what you need.

# Engine

## Overview

The **Engine** module configures the implementations used by Viem's
[cryptography utilities](/docs/utilities/hash). Viem uses portable JavaScript implementations by
default.

An Engine can replace individual primitives with WebAssembly, Node.js, or custom implementations.
The utility APIs remain unchanged.

Engine slots are partial. An omitted slot or primitive keeps its current override. When no override
exists, Viem uses its default implementation.

The loaded Ox module instance owns the registry. Each cryptographic function resolves its
implementation when called.

| Entrypoint | Behavior |
| --- | --- |
| `viem` | Manages custom or prepared Engines. [`Engine.install`](/docs/engine/install) accepts an Engine value. |
| `viem/wasm` | Compiles and installs every WebAssembly implementation supplied by the entrypoint. |
| `viem/node` | Installs every `node:crypto` implementation supplied by the entrypoint. |

```ts twoslash
import { Engine } from 'viem/wasm'
import { Hash } from 'viem/utils'

await Engine.install()

const digest = Hash.sha256('0xdeadbeef')
// @log: '0x5f78c33274e43fa9de5659265c1d917e25c03722dcb0b8d27db8d5feaa813953'
```

<Cards>
  <Card title="WASM and Engines" description="Use WebAssembly, Node.js, and custom cryptography Engines with Viem." icon="lucide:cpu" to="/docs/guides/engine" />

  <Card title="Install an Engine" description="Install a runtime Engine or a prepared set of slots." icon="lucide:download" to="/docs/engine/install" />

  <Card title="Create an Engine" description="Prepare a Node.js or WebAssembly Engine without installing it." icon="lucide:package-plus" to="/docs/engine/engine" />

  <Card title="Inspect an Engine" description="Read the currently installed overrides." icon="lucide:search" to="/docs/engine/get" />

  <Card title="Set an Engine" description="Synchronously install custom cryptographic implementations." icon="lucide:settings" to="/docs/engine/set" />

  <Card title="Reset an Engine" description="Restore one slot or every slot to its default." icon="lucide:rotate-ccw" to="/docs/engine/reset" />

  <Card title="Scope an Engine" description="Temporarily install an Engine for one synchronous function." icon="lucide:brackets" to="/docs/engine/with" />

  <Card title="Errors" description="Handle invalid slots, primitives, and asynchronous scopes." icon="lucide:circle-alert" to="/docs/engine/errors" />

  <Card title="Types" description="Reference Engine slots and primitive contracts." icon="lucide:braces" to="/docs/engine/types" />
</Cards>