# defaultIsContentTypeBinary

**Kind:** Function

**Source:** [`src/adapter/aws-lambda/handler.ts`](https://github.com/honojs/hono/blob/main/src/adapter/aws-lambda/handler.ts#L666)

**Part of:** [Adapter](subsystem-src-adapter)

Check if the given content type is binary.
This is a default function and may be overwritten by the user via `isContentTypeBinary` option in handler().

`defaultIsContentTypeBinary` checks a response `Content-Type` and returns whether AWS Lambda should treat the response body as binary data. It is the default predicate used by `handler()`, which can be replaced through the `isContentTypeBinary` handler option.

## Signature

```ts
function defaultIsContentTypeBinary(contentType: string): boolean
```

## Parameters

| Name | Type |
|---|---|
| `contentType` | `string` |

**Returns:** `boolean`

## Diagram

```mermaid
graph LR
  Response[Response Content-Type] --> Check[defaultIsContentTypeBinary]
  Check -->|binary| Encode[Base64 encode body]
  Check -->|text| Body[Return body as text]
  Override[isContentTypeBinary option] --> Check
```

## Usage

```ts
import { handler } from 'hono/aws-lambda'
import { Hono } from 'hono'

const app = new Hono()

app.get('/report', (c) => {
  return c.body(new Uint8Array([1, 2, 3]), {
    headers: {
      'Content-Type': 'application/pdf',
    },
  })
})

export const lambdaHandler = handler(app, {
  isContentTypeBinary: (contentType) =>
    contentType.startsWith('application/pdf') ||
    contentType.startsWith('image/'),
})
```

## AI Coding Instructions

- Keep the predicate input limited to the response `Content-Type` string.
- Return a boolean that determines whether the Lambda response body is Base64 encoded.
- Pass custom binary-type rules through `handler()` using `isContentTypeBinary`.
- Include custom media types when an endpoint returns non-text response bodies.