---
lang: en
title: 'API docs: boot.bootstrapper.boot'
keywords: LoopBack 4.0, LoopBack 4
sidebar: lb4_sidebar
editurl: https://github.com/strongloop/loopback-next/tree/master/packages/boot
permalink: /doc/en/lb4/apidocs.boot.bootstrapper.boot.html
---

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[Home](./index.md) &gt; [@loopback/boot](./boot.md) &gt; [Bootstrapper](./boot.bootstrapper.md) &gt; [boot](./boot.bootstrapper.boot.md)

## Bootstrapper.boot() method

Function is responsible for calling all registered Booter classes that are bound to the Application instance. Each phase of an instance must complete before the next phase is started.

<b>Signature:</b>

```typescript
boot(execOptions?: BootExecutionOptions, ctx?: Context): Promise<Context>;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  execOptions | <code>BootExecutionOptions</code> | Execution options for boot. These determine the phases and booters that are run. |
|  ctx | <code>Context</code> | Optional Context to use to resolve bindings. This is primarily useful when running app.boot() again but with different settings (in particular phases) such as 'start' / 'stop'. Using a returned Context from a previous boot call allows DI to retrieve the same instances of Booters previously used as they are bound using a CONTEXT scope. This is important as Booter instances may maintain state. |

<b>Returns:</b>

`Promise<Context>`