Brotli vs gzip Compression

Also Known As

TL;DR

Explanation

HTTP response compression reduces transfer size by 60-80% for text content (HTML, CSS, JS, JSON). gzip: universal support, good compression. Brotli: designed for web, 15-25% better compression than gzip, slightly slower to compress (pre-compress static files), supported by all modern browsers via Accept-Encoding: br. Configure at nginx/Apache level — never use PHP's ob_gzhandler() in production as it adds CPU overhead on every request without the benefits of server-level caching. Pre-compress static assets at build time.

Common Misconception

Why It Matters

Common Mistakes

• ob_gzhandler() in production PHP — use nginx/Apache compression instead.
• Not pre-compressing static assets — serve pre-built .br and .gz files directly.
• Compressing already-compressed content (images, videos) — wastes CPU with no benefit.
• No Vary: Accept-Encoding header — CDNs may serve compressed content to clients that don't support it.

Code Examples

// PHP-level compression — runs on every request:
// php.ini:
zlib.output_compression = On
// or:
ob_start('ob_gzhandler');
// CPU overhead per request, no caching, misses static file benefits

# nginx — server-level Brotli + gzip:
brotli on;
brotli_comp_level 6;
brotli_types text/plain text/css application/javascript application/json;

gzip on;
gzip_comp_level 5;
gzip_types text/plain text/css application/javascript application/json;
gzip_vary on;  # Add Vary: Accept-Encoding

# Pre-compressed static assets:
location ~* \.(js|css|html)$ {
    gzip_static on;    # Serve .gz if exists
    brotli_static on;  # Serve .br if exists
}

References

• ↗ https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding

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