Brotli vs Gzip: Which Compression Algorithm Is Better?
Brotli and Gzip are the two dominant HTTP compression algorithms used to reduce web asset sizes. Brotli, developed by Google, typically achieves 15-25% better compression than Gzip for text-based content like HTML, CSS, and JavaScript, though at the cost of slower compression speed. This page lets you test both algorithms on your own content.
Brotli / Gzip Compression Tester
Test and compare Brotli, Gzip, and Deflate compression ratios for your text content. See which algorithm gives the best compression for your data.
About Compression Testing
- Brotli — developed by Google, typically achieves 15-25% better compression than Gzip for text content. Supported by all modern browsers via HTTPS.
- Gzip — the most widely supported compression format. Based on DEFLATE algorithm. Universally supported by web servers and browsers.
- Deflate — the underlying algorithm used by both Gzip and Zlib. Lower overhead than Gzip (no header/trailer), but less common as a standalone format.
- Compression ratios vary by content type — repetitive text like JSON and HTML compresses well (70-90% savings), while already-compressed or random data may not compress at all.
- Everything runs in your browser — Gzip and Deflate use the native CompressionStream API, Brotli uses brotli-wasm. No data is sent over the network.
Key Differences Between Brotli and Gzip
Brotli uses a combination of LZ77, Huffman coding, and a predefined dictionary of common web content patterns, giving it an edge on HTML, CSS, and JavaScript. Gzip (based on DEFLATE) is faster to compress but produces larger output. For static assets served from CDNs, Brotli's superior ratio wins. For dynamic content compressed on-the-fly, Gzip's speed advantage may matter more.
Browser and Server Support
All modern browsers support both Brotli (Content-Encoding: br) and Gzip (Content-Encoding: gzip). Brotli requires HTTPS. Major CDNs like Cloudflare, AWS CloudFront, and Vercel support Brotli. Nginx, Apache, and Caddy all offer Brotli modules. The Accept-Encoding header lets servers choose the best algorithm for each client.
When to Use Each Algorithm
Use Brotli for static assets (pre-compressed at build time) where compression speed doesn't matter but file size does. Use Gzip for dynamic responses where compression must happen in real-time. Many servers use Brotli at lower quality levels (1-4) for dynamic content to balance ratio and speed. For maximum performance, serve Brotli to supporting browsers and fall back to Gzip.
Frequently Asked Questions
Is Brotli always better than Gzip?
Not always. Brotli achieves better compression ratios (15-25% smaller) but is slower to compress, especially at higher quality levels. For dynamic content that must be compressed per-request, Gzip or low-quality Brotli may be more practical. For pre-compressed static assets, Brotli is almost always the better choice.
Does Brotli work over HTTP (not HTTPS)?
No. Browsers only support Brotli over HTTPS connections. This is by design — the Brotli Content-Encoding header was introduced after HTTPS became widespread, and requiring HTTPS avoids compatibility issues with older proxies that might corrupt unknown encodings.
How much bandwidth can Brotli save compared to Gzip?
For typical web assets, Brotli saves 15-25% more bandwidth than Gzip. For HTML, the savings can be even higher (20-30%) due to Brotli's built-in dictionary of common HTML/CSS/JS patterns. For already-compressed content like images or videos, neither algorithm provides significant savings.
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