Choosing between Brotli and Gzip compression is a common decision for web developers and system administrators. Both algorithms compress text-based content effectively, but they have different strengths. This comprehensive comparison helps you understand when to use each algorithm and how to implement both for maximum compatibility and performance.

What is Gzip?

Gzip uses the DEFLATE algorithm (RFC 1951), combining LZ77 compression with Huffman coding. According to the GZIP file format specification (RFC 1952), it's been the standard for web compression since the 1990s.

Gzip is defined by Wikipedia's Gzip article as one of the most widely supported compression formats, compatible with virtually all browsers, servers, and tools.

What is Brotli?

Brotli is a modern compression algorithm developed by Google. According to Wikipedia's Brotli article, it was released in 2015 and offers 15-20% better compression ratios than gzip for text files.

Brotli uses a combination of techniques including context modeling, which makes it more effective on text-based content. The Brotli specification (RFC 7932) defines the format for HTTP content encoding.

Compression Ratio Comparison

Brotli typically achieves better compression ratios:

HTML files: Brotli 75-85% vs Gzip 60-80% (10-15% better)
CSS files: Brotli 80-90% vs Gzip 70-85% (10-15% better)
JavaScript: Brotli 70-80% vs Gzip 60-75% (10-15% better)
JSON data: Brotli 80-92% vs Gzip 75-90% (5-10% better)

According to web.dev's compression guide, Brotli provides 15-20% better compression on average, which translates to significant bandwidth savings.

Performance Comparison

Compression Speed

Gzip is generally faster at compression:

Gzip: Faster compression, especially at lower levels (1-6)
Brotli: Slower compression, but better ratios
Trade-off: Brotli's slower compression is offset by better ratios

Decompression Speed

Both algorithms decompress quickly:

Gzip: Very fast decompression
Brotli: Fast decompression, comparable to gzip
Note: Decompression speed is less critical than compression speed

CPU Usage

Brotli uses more CPU for compression:

Gzip: Lower CPU usage, especially at levels 1-6
Brotli: Higher CPU usage, but better compression
Consideration: CPU cost vs bandwidth savings

Browser Support

Browser support differs significantly:

Gzip Support:

✓ All modern browsers (100% support)
✓ Internet Explorer 6+
✓ Mobile browsers (all versions)

Brotli Support:

✓ Chrome 50+ (2016)
✓ Firefox 44+ (2016)
✓ Safari 11+ (2017)
✓ Edge 15+ (2017)
✗ Internet Explorer (not supported)

According to MDN's Content-Encoding documentation, modern browsers support both, but gzip has universal support while Brotli requires newer browsers.

When to Use Gzip

Use Gzip when:

Maximum compatibility: Need to support older browsers
High traffic: Lower CPU usage is important
Real-time compression: Need fast compression for dynamic content
Legacy systems: Working with older infrastructure
Simple setup: Want universal support without configuration

When to Use Brotli

Use Brotli when:

Better compression: Want maximum size reduction
Modern browsers: Can require newer browser support
Static content: Can pre-compress for best results
Bandwidth savings: Want to reduce data transfer costs
Mobile optimization: Reducing mobile data usage is priority

Best Practice: Use Both

The optimal strategy is to support both algorithms:

Configure server to prefer Brotli when client supports it
Fall back to Gzip for older browsers
Pre-compress static content with Brotli
Use Gzip for dynamic content (faster compression)

According to web.dev's best practices, servers should check the Accept-Encoding header and serve Brotli when available, falling back to Gzip.

Implementation Examples

NGINX Configuration

# Enable both Brotli and Gzip

brotli on;

brotli_comp_level 6;

gzip on;

gzip_comp_level 6;

# Server automatically chooses based on Accept-Encoding

Node.js/Express

Use compression middleware that supports both:

const compression = require('compression');

app.use(compression({

filter: (req, res) => {

return req.headers['accept-encoding']?.includes('br');

}

}}));

Real-World Impact

Example savings with Brotli vs Gzip:

1MB HTML file: Gzip 300KB, Brotli 250KB (50KB saved)
500KB CSS file: Gzip 100KB, Brotli 75KB (25KB saved)
2MB JavaScript: Gzip 600KB, Brotli 500KB (100KB saved)

For a typical website, Brotli can reduce total page size by 10-15% compared to Gzip, according to Google's Web Vitals research.

Conclusion

Both Brotli and Gzip are excellent compression algorithms. Gzip offers universal compatibility and faster compression, while Brotli provides better compression ratios. The best approach is to support both: use Brotli for modern browsers that support it, and fall back to Gzip for maximum compatibility. This strategy maximizes compression benefits while maintaining broad browser support.

Brotli vs Gzip: Which Compression Algorithm Should You Use?