--- title: "Brotli vs Gzip: Modern HTTP Compression Done Right (with Flask Examples)" description: "Learn when to use Brotli vs Gzip for HTTP compression. Complete implementation guide with practical examples and best practices for modern web performance." slug: "brotli-vs-gzip-modern-http-compression-done-right-with-flask-examples" url: "https://furkanbaytekin.dev/blogs/brotli-vs-gzip-modern-http-compression-done-right-with-flask-examples" author: "Furkan Baytekin" category: "Software" tags: [] published: 2025-12-21T10:15:28Z updated: 2025-12-21T10:15:28Z readTime: 3 cover: "https://myblogcms.furkanbaytekin.dev/uploads/cover/brotli-vs-gzip-modern-http-compression-done-right-with-flask-examples+1766311193632" --- Fast websites win. Compression is one of the cheapest performance gains you can get, and today the real choice is **Brotli vs Gzip**. Short version: - **Brotli** → better compression, smaller files - **Gzip** → wider legacy support - **Correct setup** → Brotli first, Gzip fallback, plain text if all else fails Let’s break it down and implement it properly. --- ## What Is HTTP Compression? HTTP compression reduces response size before sending it over the network. Flow: 1. Browser sends `Accept-Encoding` 2. Server picks the best supported algorithm 3. Response is compressed and sent with `Content-Encoding` Smaller payload = faster load = better Core Web Vitals. --- ## Brotli vs Gzip (Quick Comparison) | Feature | Brotli | Gzip | | ------------------- | --------------- | --------- | | Compression ratio | ✅ Better | ❌ Lower | | CPU cost | Slightly higher | Lower | | Static assets | Excellent | Good | | Browser support | Modern browsers | Universal | | Default in HTTP/2/3 | Common | Common | Rule of thumb: - **Use Brotli when possible** - **Fallback to Gzip** - **Never break old clients** --- ## Browser Support (Client Side) Modern browsers send this header automatically: ```http Accept-Encoding: br, gzip, deflate ``` ### Brotli Supported By - Chrome - Firefox - Edge - Safari - Mobile browsers (modern) ### Gzip Supported By - Literally everything since the stone age If `br` is present → use Brotli. If not → use Gzip. If neither → send uncompressed. --- ## Required Response Headers ### Compressed Response ```http Content-Encoding: br Vary: Accept-Encoding ``` ### Why `Vary` Matters Without it, CDNs and proxies may cache the wrong version and serve garbage. Always include: ```http Vary: Accept-Encoding ``` --- ## Flask Implementation: Brotli + Gzip + Fallback ### Install Dependencies ```bash pip install brotli ``` --- ### Basic Flask Compression Middleware ```python from flask import Flask, request, Response import gzip import brotli app = Flask(__name__) def compress_response(data: bytes, encoding: str): if encoding == "br": return brotli.compress(data), "br" if encoding == "gzip": return gzip.compress(data), "gzip" return data, None @app.after_request def apply_compression(response: Response): if response.direct_passthrough: return response accept_encoding = request.headers.get("Accept-Encoding", "") data = response.get_data() encoding = None if "br" in accept_encoding: encoding = "br" elif "gzip" in accept_encoding: encoding = "gzip" compressed, used = compress_response(data, encoding) if used: response.set_data(compressed) response.headers["Content-Encoding"] = used response.headers["Content-Length"] = len(compressed) response.headers["Vary"] = "Accept-Encoding" return response ``` --- ## Serving Compressionless Responses (Opt-Out) Some endpoints **should not** be compressed: - Streaming - SSE - Binary files - Already compressed data Example: ```python @app.route("/health") def health(): response = Response("OK") response.direct_passthrough = True return response ``` Or explicitly disable compression via header: ```python response.headers["Content-Encoding"] = "identity" ``` --- ## Static Files: Best Practice For production: - Precompress assets: - `file.js.br` - `file.js.gz` - Serve directly via CDN / reverse proxy - Flask should not handle this in production But for local or internal tools, middleware is fine. --- ## SEO Impact Compression helps SEO indirectly: - Faster TTFB - Better LCP - Lower bandwidth usage - Higher Lighthouse scores Google doesn’t care _which_ compression you use — only that your site is fast. --- ## Final Recommendation **Best setup today:** 1. Brotli for modern browsers 2. Gzip fallback 3. Plain response as last resort 4. Always set `Vary: Accept-Encoding` 5. Avoid compressing already-compressed data If you’re using a CDN later, keep this logic consistent so behavior doesn’t change. That's it. Simple, correct, future-proof. --- Album of the blog: