# Compress Middleware

This middleware compresses the response body, according to `Accept-Encoding` request header.

::: info
**Note**: On Cloudflare Workers and Deno Deploy, the response body will be compressed automatically, so there is no need to use this middleware.
:::

## Import

```ts
import { Hono } from 'hono'
import { compress } from 'hono/compress'
```

## Usage

```ts
const app = new Hono()

app.use(compress())
```

## Options

### <Badge type="info" text="optional" /> encoding: `'gzip'` | `'deflate'`

The compression scheme to allow for response compression. Either `gzip` or `deflate`. If not defined, both are allowed and will be used based on the `Accept-Encoding` header. `gzip` is prioritized if this option is not provided and the client provides both in the `Accept-Encoding` header.

### <Badge type="info" text="optional" /> threshold: `number`

The minimum size in bytes to compress. Defaults to 1024 bytes.

### <Badge type="info" text="optional" /> contentTypeFilter: `RegExp` | `(contentType: string) => boolean`

A `RegExp` or function to determine whether the response should be compressed based on its `Content-Type`. By default, a built-in list of compressible Content-Types is used.

You can pass a `RegExp` to compress only matching Content-Types:

```ts
// Compress only JSON responses
app.use(compress({ contentTypeFilter: /^application\/json/ }))
```

Or pass a function for custom logic. The built-in `COMPRESSIBLE_CONTENT_TYPE_REGEX` is also exported so you can extend the default behavior:

```ts
import {
  compress,
  COMPRESSIBLE_CONTENT_TYPE_REGEX,
} from 'hono/compress'

// Compress the default Content-Types plus a custom one
app.use(
  compress({
    contentTypeFilter: (type) =>
      COMPRESSIBLE_CONTENT_TYPE_REGEX.test(type) ||
      type === 'application/x-myformat',
  })
)
```