Brotli or gzip compression enabled on text assets

Uncompressed text assets transfer 2–5x more bytes than their compressed equivalents (ISO-25010 resource-utilisation). A 245 KB JavaScript bundle served without compression transfers 245 KB; with Brotli compression it transfers approximately 55 KB — a 78% reduction. Every kilobyte saved reduces time-to-interactive on constrained connections, cuts CDN egress costs, and directly improves LCP for users on slower networks. Brotli consistently outperforms gzip by 15–25%, making it the preferred algorithm for static text assets.

Verify compression is active by checking response headers:

curl -sI -H "Accept-Encoding: br, gzip" https://yoursite.com/js/app.js | grep -i content-encoding
# Expected: content-encoding: br  (or gzip)

For Node.js servers without a CDN or reverse proxy in front, add the compression middleware:

// server.ts
import compression from 'compression'
import express from 'express'

const app = express()
app.use(compression())  // enables gzip by default

For Brotli (better compression ratio), use shrink-ray-current instead:

import shrinkRay from 'shrink-ray-current'
app.use(shrinkRay())  // serves br for capable clients, gzip as fallback

Vercel, Netlify, and Cloudflare enable Brotli by default — no configuration needed on those platforms.

• ID: compression

• Severity: low

• What to look for: Check server response headers for Content-Encoding: gzip or Content-Encoding: br. Test with curl -H "Accept-Encoding: gzip, deflate, br". Verify that text assets (HTML, CSS, JS, JSON) are compressed. Check CDN or server configuration for compression settings.

• Pass criteria: Text assets (HTML, CSS, JS) are compressed with gzip or Brotli. Compression ratio is 40-60% (e.g., 100KB JS becomes 40KB gzipped). Response headers show Content-Encoding: gzip or br.

• Fail criteria: Text assets served uncompressed, or compression is disabled. Large files (over 100KB) transfer without compression. Response headers missing Content-Encoding.

• Skip (N/A) when: All assets are already small (under 50KB) and network bandwidth is abundant.

• Detail on fail: Specify uncompressed assets. Example: "app.js 245KB served without compression; with gzip would be 60KB. Content-Encoding header missing" or "All CSS files uncompressed; styles.css 85KB could be 20KB gzipped".

• Remediation: Enable compression on your hosting platform:

  Vercel: Enabled by default. Netlify: Enabled by default. AWS: Enable compression in CloudFront behavior settings.

  Or configure on custom servers (Node.js):

  import compression from 'compression'
  app.use(compression())