Node.js Gzip Compression Made Easy: Code Samples to Boost Performance

Overview

Anyone who has done web performance optimization is familiar with gzip, a powerful tool that compresses resources on the server before sending them to the browser, saving bandwidth and speeding up access.

The browser indicates supported compression algorithms via the Accept‑Encoding request header.

Accept-Encoding: gzip, deflate

In Node.js, the built‑in zlib module provides this functionality.

1. Entry Example

1.1 Compression Example

A few lines of code compress a local file using gzip.

var fs = require('fs');
var zlib = require('zlib');

var gzip = zlib.createGzip();

var inFile = fs.createReadStream('./extra/fileForCompress.txt');
var out = fs.createWriteStream('./extra/fileForCompress.txt.gz');
inFile.pipe(gzip).pipe(out);

1.2 Decompression Example

The reverse operation decompresses the file.

var fs = require('fs');
var zlib = require('zlib');

var gunzip = zlib.createGunzip();

var inFile = fs.createReadStream('./extra/fileForCompress.txt.gz');
var outFile = fs.createWriteStream('./extra/fileForCompress1.txt');
inFile.pipe(gunzip).pipe(outFile);

2. Server‑Side Gzip Compression

The server checks the accept‑encoding header; if it contains gzip, the response is compressed.

If not, the original file is sent.

If yes, the file is sent with gzip compression.

var http = require('http');
var zlib = require('zlib');
var fs = require('fs');
var filepath = './extra/fileForGzip.html';

var server = http.createServer(function(req, res) {
    var acceptEncoding = req.headers['accept-encoding'];
    var gzip;
    if (acceptEncoding && acceptEncoding.indexOf('gzip') !== -1) {
        // gzip compression needed
        gzip = zlib.createGzip();
        res.writeHead(200, {'Content-Encoding': 'gzip'});
        fs.createReadStream(filepath).pipe(gzip).pipe(res);
    } else {
        fs.createReadStream(filepath).pipe(res);
    }
});

server.listen('3000');

3. Server‑Side String Gzip Compression

For string responses, zlib.gzipSync can be used.

var http = require('http');
var zlib = require('zlib');

var responseText = 'hello world';

var server = http.createServer(function(req, res) {
    var acceptEncoding = req.headers['accept-encoding'];
    if (acceptEncoding && acceptEncoding.indexOf('gzip') !== -1) {
        res.writeHead(200, {'content-encoding': 'gzip'});
        res.end(zlib.gzipSync(responseText));
    } else {
        res.end(responseText);
    }
});

server.listen('3000');

4. Conclusion

The usage of deflate compression is similar; refer to the official documentation for more details.