The node:zlib module provides compression functionality implemented using Gzip, Deflate/Inflate, and Brotli.

To access it:

import zlib from 'node:zlib';

Compression and decompression are built around the Node.js Streams API.

Compressing or decompressing a stream (such as a file) can be accomplished by piping the source stream through a zlib Transform stream into a destination stream:

import { createGzip } from 'node:zlib';
import { pipeline } from 'node:stream';
import {
  createReadStream,
  createWriteStream,
} from 'node:fs';

const gzip = createGzip();
const source = createReadStream('input.txt');
const destination = createWriteStream('input.txt.gz');

pipeline(source, gzip, destination, (err) => {
  if (err) {
    console.error('An error occurred:', err);
    process.exitCode = 1;
  }
});

// Or, Promisified

import { promisify } from 'node:util';
const pipe = promisify(pipeline);

async function do_gzip(input, output) {
  const gzip = createGzip();
  const source = createReadStream(input);
  const destination = createWriteStream(output);
  await pipe(source, gzip, destination);
}

do_gzip('input.txt', 'input.txt.gz')
  .catch((err) => {
    console.error('An error occurred:', err);
    process.exitCode = 1;
  });

It is also possible to compress or decompress data in a single step:

import { deflate, unzip } from 'node:zlib';

const input = '.................................';
deflate(input, (err, buffer) => {
  if (err) {
    console.error('An error occurred:', err);
    process.exitCode = 1;
  }
  console.log(buffer.toString('base64'));
});

const buffer = Buffer.from('eJzT0yMAAGTvBe8=', 'base64');
unzip(buffer, (err, buffer) => {
  if (err) {
    console.error('An error occurred:', err);
    process.exitCode = 1;
  }
  console.log(buffer.toString());
});

// Or, Promisified

import { promisify } from 'node:util';
const do_unzip = promisify(unzip);

do_unzip(buffer)
  .then((buf) => console.log(buf.toString()))
  .catch((err) => {
    console.error('An error occurred:', err);
    process.exitCode = 1;
  });