# HTTP caching

> Headers that tell browsers and CDNs how long a response may be reused — the cheapest performance optimization that exists.

A cached response costs zero server work and zero network: Cache-Control: max-age=31536000, immutable on a fingerprinted asset like app.a1b2c3.js means the second visit loads it from disk. The web's fastest request is the one never sent.

The two failure modes mirror each other: caching mutable content (serving yesterday's prices) and not caching immutable content (re-downloading the same bundle on every visit). The fix is naming — fingerprinted filenames can be cached forever because a change produces a new name — plus short, revalidated lifetimes on HTML.

## Related terms

- https://dfieldsolutions.com/en/glossary/cdn.md
- https://dfieldsolutions.com/en/glossary/lcp.md
- https://dfieldsolutions.com/en/glossary/static-generation.md

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Source: https://dfieldsolutions.com/en/glossary/http-caching
DField Solutions — Dunakeszi, Hungary — dezso@dfieldsolutions.com
Booking: see https://dfieldsolutions.com/en/contact