@fastify/compress

Adds compression utils to the Fastify reply object and a hook to decompress requests payloads. Supports gzip, deflate, and brotli.

Important note: since @fastify/compress version 4.x payloads that are compressed using the zip algorithm are not automatically uncompressed anymore. @fastify/compress main feature is to provide response compression mechanism to your server, however the zip format does not appear in the IANA maintained Table of Content Encodings and thus such behavior was out of the scope of this plugin.

Install

npm i @fastify/compress

Compatibility

Plugin version	Fastify version
^8.x	^5.x
^6.x	^4.x
^3.x	^3.x
^2.x	^2.x
^0.x	^1.x

Please note that if a Fastify version is out of support, then so are the corresponding versions of this plugin in the table above. See Fastify's LTS policy for more details.

Usage - Compress replies

This plugin adds two functionalities to Fastify: a compress utility and a global compression hook.

Currently, the following encoding tokens are supported, using the first acceptable token in this order:

1. br
2. gzip
3. deflate
4. * (no preference — @fastify/compress will use gzip)
5. identity (no compression)

If an unsupported encoding is received or if the 'accept-encoding' header is missing, it will not compress the payload. If an unsupported encoding is received and you would like to return an error, provide an onUnsupportedEncoding option.

The plugin automatically decides if a payload should be compressed based on its content-type; if no content type is present, it will assume application/json.

Global hook

The global compression hook is enabled by default. To disable it, pass the option { global: false }:

await fastify.register(
  import('@fastify/compress'),
  { global: false }
)

Remember that thanks to the Fastify encapsulation model, you can set a global compression, but run it only in a subset of routes if you wrap them inside a plugin.

Important note! If you are using @fastify/compress plugin together with @fastify/static plugin, you must register the @fastify/compress (with global hook) before registering @fastify/static.

Per Route options

You can specify different options for compression per route by passing in the compress options on the route's configuration.

await fastify.register(
  import('@fastify/compress'),
  { global: false }
)

// only compress if the payload is above a certain size and use brotli
fastify.get('/custom-route', {
  compress: {
    inflateIfDeflated: true,
    threshold: 128,
    zlib: {
      createBrotliCompress: () => createYourCustomBrotliCompress(),
      createGzip: () => createYourCustomGzip(),
      createDeflate: () => createYourCustomDeflate()
    }
  }, (req, reply) => {
    // ...
  })

Note: Setting compress = false on any route will disable compression on the route even if global compression is enabled.

reply.compress

This plugin adds a compress method to reply that accepts a stream or a string, and compresses it based on the accept-encoding header. If a JS object is passed in, it will be stringified to JSON. Note that the compress method is configured with either the per route parameters if the route has a custom configuration or with the global parameters if the the route has no custom parameters but the plugin was defined as global.

import fs from 'node:fs'
import fastify from 'fastify'

const app = fastify()
await app.register(import('@fastify/compress'), { global: false })

app.get('/', (req, reply) => {
  reply
    .type('text/plain')
    .compress(fs.createReadStream('./package.json'))
})

await app.listen({ port: 3000 })

Compress Options

threshold

The minimum byte size for a response to be compressed. Defaults to 1024.

await fastify.register(
  import('@fastify/compress'),
  { threshold: 2048 }
)

customTypes

mime-db is used to determine if a content-type should be compressed. You can compress additional content types via regular expression or by providing a function.

await fastify.register(
  import('@fastify/compress'),
  { customTypes: /x-protobuf$/ }
)

or

await fastify.register(
  import('@fastify/compress'),
  { customTypes: contentType => contentType.endsWith('x-protobuf') }
)

onUnsupportedEncoding

When the encoding is not supported, a custom error response can be sent in place of the uncompressed payload by setting the onUnsupportedEncoding(encoding, request, reply) option to be a function that can modify the reply and return a string | Buffer | Stream | Error payload.

await fastify.register(
  import('@fastify/compress'),
  {
    onUnsupportedEncoding: (encoding, request, reply) => {
      reply.code(406)
      return 'We do not support the ' + encoding + ' encoding.'
    }
  }
)

Disable compression by header

You can selectively disable response compression by using the x-no-compression header in the request.

Inflate pre-compressed bodies for clients that do not support compression

Optional feature to inflate pre-compressed data if the client does not include one of the supported compression types in its accept-encoding header.

await fastify.register(
  import('@fastify/compress'),
  { inflateIfDeflated: true }
)

fastify.get('/file', (req, reply) =>
  // will inflate the file  on the way out for clients
  // that indicate they do not support compression
  reply.send(fs.createReadStream('./file.gz')))

Customize encoding priority

By default, @fastify/compress prioritizes compression as described at the beginning of §Usage - Compress replies. You can change that by passing an array of compression tokens to the encodings option:

await fastify.register(
  import('@fastify/compress'),
  // Only support gzip and deflate, and prefer deflate to gzip
  { encodings: ['deflate', 'gzip'] }
)

brotliOptions and zlibOptions

You can tune compression by setting the brotliOptions and zlibOptions properties. These properties are passed directly to native node zlib methods, so they should match the corresponding class definitions.

  server.register(fastifyCompress, {
    brotliOptions: {
      params: {
        [zlib.constants.BROTLI_PARAM_MODE]: zlib.constants.BROTLI_MODE_TEXT, // useful for APIs that primarily return text
        [zlib.constants.BROTLI_PARAM_QUALITY]: 4, // default is 4, max is 11, min is 0
      },
    },
    zlibOptions: {
      level: 6, // default is typically 6, max is 9, min is 0
    }
  });

Manage Content-Length header removal with removeContentLengthHeader

By default, @fastify/compress removes the reply Content-Length header. You can change that by setting the removeContentLengthHeader to false either on a global scope or on a route specific scope.

  // Global plugin scope
  await server.register(fastifyCompress, { global: true, removeContentLengthHeader: false });

  // Route specific scope
  fastify.get('/file', {
    compress: { removeContentLengthHeader: false }
  }, (req, reply) =>
    reply.compress(fs.createReadStream('./file.gz'))
  )

Usage - Decompress request payloads

This plugin adds a preParsing hook that decompress the request payload according to the content-encoding request header.

Currently, the following encoding tokens are supported:

1. br
2. gzip
3. deflate

If an unsupported encoding or and invalid payload is received, the plugin will throw an error.

If the request header is missing, the plugin will not do anything and yield to the next hook.

Global hook

The global request decompression hook is enabled by default. To disable it, pass the option { global: false }:

await fastify.register(
  import('@fastify/compress'),
  { global: false }
)

Remember that thanks to the Fastify encapsulation model, you can set a global decompression, but run it only in a subset of routes if you wrap them inside a plugin.

Per Route options

You can specify different options for decompression per route by passing in the decompress options on the route's configuration.

await fastify.register(
  import('@fastify/compress'),
  { global: false }
)

// Always decompress using gzip
fastify.get('/custom-route', {
  decompress: {
    forceRequestEncoding: 'gzip',
    zlib: {
      createBrotliDecompress: () => createYourCustomBrotliDecompress(),
      createGunzip: () => createYourCustomGunzip(),
      createInflate: () => createYourCustomInflate()
    }
  }
}, (req, reply) => {
    // ...
  })

requestEncodings

By default, @fastify/compress accepts all encodings specified at the beginning of §Usage - Decompress request payloads. You can change that by passing an array of compression tokens to the requestEncodings option:

await fastify.register(
  import('@fastify/compress'),
  // Only support gzip
  { requestEncodings: ['gzip'] }
)

forceRequestEncoding

By default, @fastify/compress chooses the decompressing algorithm by looking at the content-encoding header, if present.

You can force one algorithm and ignore the header at all by providing the forceRequestEncoding option.

Note that if the request payload is not compressed, @fastify/compress will try to decompress, resulting in an error.

onUnsupportedRequestEncoding

When the request payload encoding is not supported, you can customize the response error by setting the onUnsupportedEncoding(request, encoding) option to be a function that returns an error.

await fastify.register(
  import('@fastify/compress'),
  {
     onUnsupportedRequestEncoding: (request, encoding) => {
      return {
        statusCode: 415,
        code: 'UNSUPPORTED',
        error: 'Unsupported Media Type',
        message: 'We do not support the ' + encoding + ' encoding.'
      }
    }
  }
)

onInvalidRequestPayload

When the request payload cannot be decompressed using the detected algorithm, you can customize the response error setting the onInvalidRequestPayload(request, encoding) option to be a function that returns an error.

await fastify.register(
  import('@fastify/compress'),
  {
    onInvalidRequestPayload: (request, encoding, error) => {
      return {
        statusCode: 400,
        code: 'BAD_REQUEST',
        error: 'Bad Request',
        message: 'This is not a valid ' + encoding + ' encoded payload: ' + error.message
      }
    }
  }
)

Note

Please note that in large-scale scenarios, you should use a proxy like Nginx to handle response compression.

Acknowledgements

Past sponsors:

• LetzDoIt

License

Licensed under MIT.