brotli-asgi

BrotliMiddleware adds Brotli response compression to ASGI applications (Starlette, FastAPI, Quart, etc.). It provides faster and more dense compression than GZip, and can be used as a drop in replacement for the GZipMiddleware shipped with Starlette.

Installation

pip install brotli-asgi

Examples

Starlette

from starlette.applications import Starlette
from starlette.responses import JSONResponse
from starlette.routing import Route
from starlette.middleware import Middleware

from brotli_asgi import BrotliMiddleware

async def homepage(request):
    return JSONResponse({"data": "a" * 4000})

app = Starlette(
  routes=[Route("/", homepage)],
  middleware=[Middleware(BrotliMiddleware)],
)

FastAPI

from fastapi import FastAPI
from brotli_asgi import BrotliMiddleware

app = FastAPI()
app.add_middleware(BrotliMiddleware)

@app.get("/")
def home() -> dict:
    return {"data": "a" * 4000}

API Reference

Overview

app.add_middleware(
  BrotliMiddleware,
  quality=4,
  mode="text",
  lgwin=22,
  lgblock=0,
  minimum_size=400,
  gzip_fallback=True
)

Parameters:

• (Optional) quality: Controls the compression speed vs compression density tradeoff. The higher the quality, the slower the compression. Range is 0 to 11.
• (Optional) mode: The compression mode can be: "generic", "text" (Default for UTF-8 format text input) or "font" (for WOFF 2.0).
• (Optional) lgwin: Base 2 logarithm of the sliding window size. Range is 10 to 24.
• (Optional) lgblock: Base 2 logarithm of the maximum input block size. Range is 16 to 24. If set to 0, the value will be set based on the quality.
• (Optional) minimum_size: Only compress responses that are bigger than this value in bytes.
• (Optional) gzip_fallback: If True, uses gzip encoding if br is not in the Accept-Encoding header.

Notes:

• It won't apply Brotli compression on responses that already have a Content-Encoding set, to prevent them from being encoded twice.
• If the GZip fallback is applied, and the response already had a Content-Encoding set, the double-encoding-prevention will only happen if you're using Starlette >=0.22.0 (see the PR).

Performance

To better understand the benefits of Brotli over GZip, see, Gzip vs. Brotli: Comparing Compression Techniques, where detailed information and benchmarks are provided.

A simple comparative example using Python sys.getsizof() and timeit:

# ipython console
import gzip
import sys

import brotli
import requests

page = requests.get("https://github.com/fullonic/brotli-asgi").content
%timeit brotli.compress(page, quality=4)
# 1.83 ms ± 43 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
sys.getsizeof(brotli.compress(page, quality=4))
# 20081
%timeit gzip.compress(page, compresslevel=6)
# 2.75 ms ± 29.8 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
sys.getsizeof(gzip.compress(page, compresslevel=6))
# 20640

Compatibility

According to caniuse.com, Brotli is supported by all major browsers with a global use of over 96.3%.