Speed Medium impact Easy 15–30 min

Browser caching

Static files should be stored at the visitor's end.

What it is

Browser caching (via Cache-Control / Expires headers) lets the browser store static files (images, CSS, JS, fonts) and not re-download them on the next visit.

Why it matters

Without caching, a returning visitor downloads everything again on every load, which is needlessly slow and data-heavy. Proper caching significantly speeds up repeat visits and offloads the server.

How to do it

1Set a long cache (e.g. 1 year) for immutable static files.
2Use "cache busting": versioning in the name (app.4f3a.js) so the user gets the new version on change.
3Keep HTML with a short or no cache (it must be current).
4Verify the Cache-Control headers in the response.

Caching static files (.htaccess)

Correct

<IfModule mod_expires.c>
  ExpiresActive On
  ExpiresByType image/webp "access plus 1 year"
  ExpiresByType text/css "access plus 1 year"
  ExpiresByType application/javascript "access plus 1 year"
</IfModule>

Conclusion

Browser caching is a cheap way to speed up repeat visits. The key is combining a long cache for static assets + versioned names so you can change files without the risk of the user seeing an old version. Keep HTML fresh, on the other hand.