Cache Freshness and Revalidation

HTTP caches decide whether a stored response is fresh, stale, or reusable after validation.

Use Cache-Control for freshness, ETag or Last-Modified for validation, and no-store for data that must not be stored. no-cache means revalidate, not do not store.

httpcacheperformanceconditional

Reference (http)

Cache-Control: max-age=60, stale-while-revalidate=30
ETag: "v7"

Use Cache-Control for freshness, ETag or Last-Modified for validation, and no-store for data that must not be stored. no-cache means revalidate, not do not store.

Common mistakes

Using no-cache when the requirement is to prevent storage entirely.

Cache-Control: stale-while-revalidate Cache-Control: stale-if-error Cache-Control: immutable ETag and Conditional Requests

Sources

MDN HTTP Reference