Cache-Control header check

Grades your Cache-Control headers on static assets, HTML, and API responses — bad caching is a leading hidden cause of slow LCP.

Quick answer

Lemwatch samples 20 assets per page load and grades Cache-Control against Google's recommendations.

What it checks

• Static assets: max-age ≥ 1 year + immutable
• HTML: no-cache or short max-age
• API JSON: private + short max-age
• Missing Cache-Control (worst case) flagged

Where to find it in Lemwatch

Site details → Performance → Caching.

How to fix

1. Fingerprint asset filenames (app.abc123.js).
2. Serve fingerprinted assets with Cache-Control: public, max-age=31536000, immutable.
3. HTML gets Cache-Control: no-cache so users see deploys immediately.
4. Re-run.

FAQ

Is immutable safe?

Yes — as long as filenames change on every deploy.

What about ETag?

Still useful, but Cache-Control is the primary signal.

Related

• Performance budgets
• Gzip/Brotli compression check
• Core Web Vitals