How do you implement request/response compression in Express.js?

Question

Accepted Answer

**Compression** — reduces response size for faster transfers.

```javascript
const compression = require("compression");

app.use(compression({
    level: 6,           // compression level (1-9)
    threshold: 1024,    // minimum size to compress
    filter: (req, res) => {
        if (req.headers["x-no-compression"]) return false;
        return compression.filter(req, res);
    },
}));

// Manual compression
const zlib = require("zlib");

app.get("/data", (req, res) => {
    const data = JSON.stringify(largeObject);

const accepted = req.headers["accept-encoding"];

if (accepted.includes("br")) {
        res.setHeader("Content-Encoding", "br");
        res.send(zlib.brotliCompressSync(data));
    } else if (accepted.includes("gzip")) {
        res.setHeader("Content-Encoding", "gzip");
        res.send(zlib.gzipSync(data));
    } else if (accepted.includes("deflate")) {
        res.setHeader("Content-Encoding", "deflate");
        res.send(zlib.deflateSync(data));
    } else {
        res.send(data);
    }
});
```

**Brotli vs Gzip:**
- Brotli: better compression, slower.
- Gzip: faster, good enough.
- Use compression middleware for simplicity.

Node.js: How do you implement request/response compression in Express.js?