I have read that I should be compressing requests to my Node server, so I used npm to install the compression module, added it with require() to my server.js, then passed it in as a function to app.use.

Then I looked at the network tab after, and I wanted to see how much the compression had saved me in kb. So I took the compression off, restarted my server, and it was the same amount of kb as with compression turned on?

Here is my server.js

var express = require('express'),
    app = express(),
    path = require('path'),
    apiRouter = require('./app/routes/api'),
    mongoose = require('mongoose'),
    compression = require('compression');

app.use(compression());
app.use(express.static('public'));
app.use('/api', apiRouter);

app.use('*', function(req, res) {
    res.sendFile(path.join(__dirname + '/public/index.html'));
});

mongoose.connect('mongodb://localhost/triviaattack');

var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
    //Connected to DB successfully.

});

app.listen(1337);

I have read that I should be compressing requests to my Node server, so I used npm to install the compression module, added it with require() to my server.js, then passed it in as a function to app.use.

Then I looked at the network tab after, and I wanted to see how much the compression had saved me in kb. So I took the compression off, restarted my server, and it was the same amount of kb as with compression turned on?

Here is my server.js

var express = require('express'),
    app = express(),
    path = require('path'),
    apiRouter = require('./app/routes/api'),
    mongoose = require('mongoose'),
    compression = require('compression');

app.use(compression());
app.use(express.static('public'));
app.use('/api', apiRouter);

app.use('*', function(req, res) {
    res.sendFile(path.join(__dirname + '/public/index.html'));
});

mongoose.connect('mongodb://localhost/triviaattack');

var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
    //Connected to DB successfully.

});

app.listen(1337);

• javascript
• node.js
• express
• compression

• Edited my question, accidentally posted the version of server.js without the compression module. Fixed. – JohnWick Commented Jan 19, 2016 at 8:42

3 Answers 3

Compression does not work unless the client sends a "Accept-Encoding:gzip" request header. You can test the compression here.

When turning compression on and off for testing make sure that you're doing a hard reload in chrome dev tools or otherwise you'll get a 'not-modified' response that is not compressed.

Your example code is working for me!

The compression middleware is a demanding horseman.

You need to set two things for it to work:

On the server, you need to specify a threshold size in bytes (default is 1024 (1kb) ) beyond which the response will be compressed. Start with 0:

app.use(compression({
    threshold: 0
}))

On the client, you need to set a header called Accept-Encoding to 'gzip' .

GET /mimic HTTP/1.1
Accept-Encoding: gzip
Host: localhost:3005

To decompress a response from the client side, you can do sth like this:

    const response = await axios.post(
        'http://localhost:3005/mimic', { headers: { "Accept-Encoding": "gzip" }, responseType: 'arraybuffer' })
    const xmlData = zlib.gunzipSync(response.data).toString()

In the above code, I am using the zlib and axios modules. zlib is a nodejs builtin module. There are other approaches if you're doing it from the browser. Notice that response.data is an array buffer.