@fastify/compress

Compress responses on the fly with gzip, brotli, or deflate, negotiated through the client's Accept-Encoding header.

4 min read Level 2/5 #fastify#compress#performance

What you'll learn

Install @fastify/compress
Register with default settings
Tune the threshold to skip compressing small payloads

Most JSON APIs benefit from compression — a 50 KB response often shrinks to 10 KB. @fastify/compress negotiates the algorithm with the client and pipes the response through a transform stream.

Install & Register

npm install @fastify/compress

import compress from '@fastify/compress'

await app.register(compress, {
  threshold: 1024,
  encodings: ['br', 'gzip', 'deflate'],
})

The encodings order is the preference order — brotli first, gzip second. threshold: 1024 skips compression for payloads under 1 KB, where the overhead is greater than the saving.

Streamed Responses

Compression works on streams too. Wrap a file or generator response and the plugin compresses chunk-by-chunk.

import { createReadStream } from 'node:fs'

app.get('/big.csv', async (req, reply) => {
  reply.type('text/csv')
  return createReadStream('./reports/big.csv')
})

Skipping Routes

For already-compressed assets (images, video, fingerprinted JS served by a CDN) you don’t want a second pass. Skip per-route:

app.get('/raw', { compress: false }, async () => {
  return { tiny: 'payload' }
})

The plugin also auto-skips common binary types like image/png and video/mp4.

@fastify/formbody →