Compression

Compression can significantly reduce the size of the response body, which makes a web app faster to load.

For high-traffic websites in production, we strongly recommend offloading compression from the application server, typically to a reverse proxy (e.g., Nginx). In that case, don't use compression middleware.

Use with Express (default)#

Use the compression middleware package to enable response compression. It supports the gzip, deflate, and Brotli encodings, and picks one based on the request's Accept-Encoding header.

First, install the required packages:

$ npm i --save compression
$ npm i --save-dev @types/compression

Once the installation is complete, apply the compression middleware globally:

import compression from 'compression';
// somewhere in your initialization file
app.use(compression());

Use with Fastify#

If you use the FastifyAdapter, use the @fastify/compress plugin instead:

$ npm i --save @fastify/compress

Once the installation is complete, register the @fastify/compress plugin. It compresses all eligible responses by default.

Warning Make sure you pass the NestFastifyApplication type when creating the application. Otherwise, the register() method isn't available to apply the plugin.

import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';

import compression from '@fastify/compress';

// inside bootstrap()
const app = await NestFactory.create<NestFastifyApplication>(AppModule, new FastifyAdapter());
await app.register(compression);

By default, @fastify/compress uses the first encoding the client accepts, in this order of preference: zstd (on Node.js versions that support it), br (Brotli), gzip, and deflate. Brotli achieves a high compression ratio, but higher quality levels are slow. The plugin sets the Brotli quality (BROTLI_PARAM_QUALITY) to 4 by default instead of zlib's default of 11. You can set it anywhere from 0 (fastest) to 11 (smallest output), trading compression time against response size. Tune this value for your workload. The following example sets the quality explicitly:

import { constants } from 'node:zlib';
// somewhere in your initialization file
await app.register(compression, { brotliOptions: { params: { [constants.BROTLI_PARAM_QUALITY]: 4 } } });

Alternatively, you can restrict @fastify/compress to gzip and deflate. Responses may be larger, but they are compressed faster.

To specify the encodings, pass the encodings option in the second argument to app.register():

await app.register(compression, { encodings: ['gzip', 'deflate'] });

This configuration tells @fastify/compress to use only the gzip and deflate encodings, preferring gzip when the client supports both.