Browser Cache

Browser cache is a copy of assets (CSS, JS, images, fonts) stored on the visitor's device. On a return visit, the browser can use the local copy without asking the server again.

The headers that control it

A common example:

Cache-Control: public, max-age=31536000, immutable

Use it for assets whose filenames contain a hash (app.3f9c2.js). For HTML, use no-cache or a short max-age so changes appear quickly.

Cache busting

If the filename stays the same, the browser may keep using the old version. Change the filename during the build (app.[hash].js) or add a version query. Do not rely on ?v=1 for every asset without changing it on deploy.

What to watch for

• Browser cache and CDN cache are different. Each has its own rules.
• Do not cache old HTML. Pages can show stale content after a deploy.
• Use no-store for sensitive data. Do not put account pages in a public cache.
• Test after deploy. A hard reload or Incognito helps confirm the new version.
• 304 is a healthy response. The browser uses its cache and the server saves bandwidth.

Every deploy should produce new asset filenames. If HTML is cached too long, visitors can see links to old assets that no longer exist. Test in Incognito after deploy and keep HTML and static-asset Cache-Control policies separate.

FAQ