Optimizing Your Express.js Application with Brotli Compression: A Guide to Effective Configuration

In today’s performance-driven web environment, effective compression techniques are essential to improve load times and enhance user experience. While gzip has long been the standard for server-side compression, Brotli (br) is increasingly popular due to its superior compression ratios, especially for text-based content. If you’re working with an Express.js application and want to implement Brotli compression, but find yourself struggling with configuration issues, this guide will help clarify best practices and troubleshoot common pitfalls.

Understanding the Challenge

Many developers aim to compare Brotli’s performance directly against gzip, but integrating Brotli into an existing Express.js setup can be tricky. Common issues include:

• Incomplete or incorrect middleware configuration
• Client request headers not negotiating Brotli compression
• External modules or dependencies not installed or compatible
• Misaligned server and client expectations regarding ‘accept-encoding’ headers

It’s worth noting that some middleware modules like ‘shrink-ray’ or ‘compression’ may have limitations or specific configurations needed to support Brotli. As you’ve observed, adding extra modules isn’t always feasible or desirable, so configuring what’s available correctly becomes crucial.

Your Current Setup

Based on your description, you’re using the ‘compression’ middleware with a configuration similar to:

javascript
app.use(compression({
enforceEncoding: 'br',
brotli: {
enabled: true,
params: {
[zlib.constants.BROTLI_PARAM_QUALITY]: 4
}
},
filter: (req, res) => true
}));

And your client request includes:

accept-encoding: gzip, deflate, br, zstd

Analyzing Your Configuration

1. Middleware Selection:
   The ‘compression’ package is widely used, but its support for Brotli depends on the version and the underlying ‘zlib’ capabilities. Make sure you’re using a version of ‘compression’ that supports Brotli, or consider using a different middleware known for Brotli support, like ‘iltorb’ or native Node.js compression APIs.

2. EnforceEncoding Flag:
   The ‘enforceEncoding’ option isn’t officially documented in the ‘compression’ package. Instead, setting ‘threshold’, ‘filter’, and other options are common. Verify if ‘enforceEncoding’ is supported or if it’s part of a custom extension.

3. Brotli Enablement and Parameters: